This diminutive mechanical clock is designed for a very unusual role, recording timestamps in a film based "gun camera" mounted to the side of a military aircraft. Gun cameras were used on military aircraft to record damage to enemy targets, and military intelligence specialists found it useful to have a timestamp attached to each photo. To provide this, a small clock would be mounted inside the camera; a series of prisms would superimpose the clock face in a corner of the camera's field of view, which would then be recorded every time the camera took a picture. This clock makes use of an Elgin 685 movement, a movement type that is typically used for 24 hour wristwatches. Some gun camera clocks are electrically wound, but this clock has an external crown for winding and setting similar to the type found on a wristwatch. In operation the clock would be mounted in a removable compartment on the camera and would need to be wound and set before the start of a mission.

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A time lock is a special type of clock designed to be mounted inside of a bank vault or high-security safe. Time locks are designed to prevent robberies by sealing a bank vault until a designated amount of time passes, which prevents a potential robber from kidnapping the bank manager after hours and forcing him or her to open the vault door. This time lock mechanism, manufactured by Eaton, is a typical example of the style of time lock used during the Cold War. The lock contains two complete and separate spring-driven clock movements for redundancy, either movement can trigger the lock's release mechanism. Each movement has a dial with a small pin attached that indicates the amount of time remaining before the vault can be opened; the pins engage levers along the bottom of the movement that free the bolt on the vault door when the dials are at the zero position. Note that in the thumbnail the cover and bolt-work for the lock have been removed to allow the movements to be seen. The dials are set and the movements wound with a key that inserted through a pair of small holes on the face of the lock.

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This unusual device is the clock out of a MD-1 Astro Navigation system, which was the navigation system used on B-52 bombers prior to the invention of inertial guidance systems. Sometimes called the Star Tracker system, this complicated device made use of an electromechanical sextant mounted to the top of the aircraft, linked to an array of controls and computer modules. When in operation the Astro Navigation system would track the positions of up to three stars (or the Sun), and calculate the aircraft's current position. This clock is powered by a 28 volt, 400hz synchronous motor which also serves as the device's timebase. The clock contains no external setting controls, but a complicated system of synchro transmitters and synchronous motors allow the clock to be set and read by the star tracker system. In normal operation this clock would have been sealed in an airtight gas filled enclosure, and a valve stem has been attached to the back panel of the clock to allow filling and removal of gas after the case is sealed.

When first released, the clock in the MD-1 Astro Navigation system was notoriously inaccurate. This was solved in later versions by the addition of a new tuning fork timebase, which supplied a clean 400Hz signal to the clock's synchronous motor.

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The Yale Triple L is an ornate, early mechanical timelock designed for use in smaller safes and vault doors. Called such because it contained three Type L movements, the Triple L is one of the most common early timelocks, with more than 16,000 units being produced. The earliest Triple L time locks had nickel plated cases and an all glass front door with metal escutcheons for the winding holes. These did not see widespread use however, and Yale soon switched to the much more common half metal door used in this example. The door is secured with a key to prevent employee tampering, and contains three holes which allow the timelock movements inside to be wound and set. Each movement contains 11 jewels and is marked with a serial number that is reproduced on all the major parts of the movement, which makes it easy to identify movements which have had parts replaced. This model of timelock was produced from 1892 to 1920 with the example shown here having been built sometime after 1908.

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The Consolidated Time Lock company was a prolific manufacturer of time locks from 1880 until 1906, and made use of many different models of time lock movements during that period. Dalton time lock movements of this type were produced from between 1905 and 1906 for use in Consolidated two and three movement time lock mechanisms. The movement itself consists of a South Bend size 18 pocketwatch movement connected to a large external mainspring and readout dial.The entire assembly is mounted in a heavy nickel-plated brass enclosure. This timelock movement can operate on a delay of up to 76 hours; the small metal tab at the bottom of the dial interfaces with the rest of the time lock, and will move to the left when the movement's dial reaches zero. Originally the watch movement would have been protected behind a transparent glass crystal, but the crystal is long since lost on this example. Like most time locks, this Dalton movement is made to an exceptional level of quality, with polished nickel plating and engraving work covering every outside-facing surface.

H. M. Dalton produced these timelock movements for only three years, from 1904 to 1906. Earlier movements, produced in 1904, can be easily identified by their white porcelain dials. These movements make use of Elgin pocketwatch movements with a Consolidated badge mounted over the pillar plate. Movements made from 1905 to 1906 are equipped with black dials and South Bend pocketwatch movements. In 1906 Dalton ceased production when the Consolidated Time Lock company was bought out by Victor Safe Lock, though it is believed that this design may have been refined and used in Banker's Dustproof time locks, which entered production in 1907.

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Back in the hallowed days of our transistor-anemic past, turning light bulbs on and off at preset times was a seriously complicated task - so much so that when the City of New York was hard-up for a way to control its streetlights automatically, they made the dubious decision to mount metal-clad Telechron clocks to every street corner. These devices, manufactured by General Electric, were encased in a heavy vandal-resistant cast case and have a complex internal mechanism that implements a 365 day calendar and automatic daylight compensation. The metal pins that operate the time switch are mounted to a pair of rotating levers that move independently of the main dial. These levers are positioned by a 364 tooth calendar gear that completes one rotation relative to the main dial every year, allowing the switch to automatically match the operating time of the streetlamp to the length of the day.

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Sargent & Greenleaf is a prolific manufacturer of time locks and time lock components, and the Type L movement is a typical example of the type of movements used in older Sargent & Greenleaf time locks. Unlike most manufacturers of this era, which used movements manufactured by the E. Howard watch company, Sargent & Greenleaf constructed their own movements in-house. As a result, Sargent & Greenleaf time lock movements contain many distinctive design choices, such as a characteristic 'wagon wheel'-style dial and an unusual jeweled escapement that does not include a roller gem on the balance wheel. These movements were designed to be used in groups for redundancy; typically two or three movements would be installed in a single time lock. Sargent & Greenleaf made both brass and nickel plated versions of this time lock movement, which are functionally identical other than the choice of metal used in their construction. We have been unable to accurately date this item, but suspect it was manufactured sometime between 1890 and 1920.

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World War 2 and the buildup immediately preceeding it saw the manufacture of numerous different types of aircraft clocks, and this Longines Wittnauer A7 clock is one such example. A7 model clocks differ from the much more common A6 model in that they have a 'pendant wind' winding stem which exits the bottom of the case instead of extending vertically below the 6-o-clock position. A metal plug has been pressed into the winding stem hole that would have been used in an A6 model clock. This clock makes use of a Jaeger LeCoultre 201M caliber movement, a relatively high end time-only movement with a 7 jewel lever escapement. This model of clock was also manufactured with a less common and more expensive 14 jewel movement.

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This unusual clock is a complicated mechanical device, one which combines the functions of a timepiece, printing press, and secure storage facility... all for the singular purpose of settling bets over which pigeon is the fastest. Manufactured by Plasschaert, this specialized machine is used to time pigeon races, and its sheer complexity suggests pigeon racing is a much more contentious hobby than one might expect. The heart of the device is a rotating brass carousel, which is equipped with an array of small numbered compartments. When sealed inside of it's locked wooden carrying case, only a single compartment can be accessed at a time through a small trapdoor in the top of the device. In operation, a numbered band is removed from the leg of each pigeon as it crosses the finish line and placed into the open compartment. Turning a large T-shaped handle on the top of the clock will retract the current compartment into the device, while simultaneously moving a new compartment into position below the trapdoor and printing the current time onto a paper register inside the clock's sealed wooden case. The high quality movement within the Plasschaert No 3 is equipped with two clock faces; one is readable through a glass window on the front of the device, while the second takes the form of a metal printing press plate with movable vanes for each of the clock's four dials. Once the current time has been printed on the paper register, another turn of the T-handle will move the most recent print to a glass window where it can be viewed by the operator. A third small glass strip on the opposite side of the device allows the current state of the paper roll to be viewed.

The Plasschaert No 3 contains a number of features designed to prevent unscrupulous pigeon racers from tampering with the clock's results. A security mechanism mounted on the right side of the printing press punches a hole in the paper register every time the lid is opened. Additionally, the balance wheel platform has an extra set of gearing attached to a spring loaded weight. If the clock is shaken or spun rapidly to try to speed up or slow down the movement, the weight will release and freeze the time on the clock face. A small button on the top of the clock movement, which is only accessible when the case is open, will reset this security lockout feature. Winding and setting of the clock is done through a series of holes and arbors on the clock's dial, which is also only accessible when the case is unlocked and open.

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Back in the time before Uber and digital electronics, taxi drivers would make use of elaborate mechanical taximeters. These devices, which were typically mounted between the driver and passenger seat of a taxi, contained a complex mechanical integrator which would combine time and distance traveled to calculate the fare a customer would pay for a trip. The example shown here, manufactured in the mid 1930s by the Ohmer Fare Register company of Dayton Ohio, has had it's cover removed so the internal mechanism can be seen. The bottom half of the machine contains a brass clock movement and a connection that linked to the taxi's odometer by means of a flexible cable. The integrated outputs from these two systems would advance a large mechanical counter on the front of the device; this would face the passenger when installed between the seats of a taxi.

The inside of this fare register is a dense forest of cogs and stamped steel levers worthy of a tired Rube Goldberg comparison. The only electrical component in the entire mechanism is a single leaf switch on the side of the device. This switch closes when the driver turns off the taximeter, and would connect to a lamp on the roof of the taxi to indicate that it is 'available' to potential customers. While much less convenient than a smartphone app, such a system does have the benefit of being completely free of pop-up ads and viral internet cat videos.

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Before the global microprocessor invasion, Sangamo synchronous time switches were the definitive method for controlling exterior lamps and other electrical devices that would need to be powered on and off in accordance with a pre-determined schedule. Sangamo time switches contain a large electromechanical clock movement that drives a rotating metal disk. The disk has a number of movable 'fingers', which varies from model to model: the KA-21 is equipped with six, while the WA-21 has only four. The schedule is set by moving the fingers around the disk to the appropriate time. As the disk makes a revolution, the fingers push mechanical levers which open and close a set of electrical contacts.

Both the KA-21 and WA-21 have a rectangular glass window on their face to verify the set schedule, as well as a smaller, circular window for observing the synchronous motor in operation.

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Sangamo produced many specialized timers beyond it's conventional 24 hour time switch products... this unusual device is a single shot countdown timer that can close a set of contacts up to 145 days in the future. Two different times can be set on the CD-14's multipart dial; a start date and an 'armed' date. When the armed date is reached a set of contacts is closed by a spring-loaded lever, and a second set of contacts is closed when the start date is reached, up to 145 days later. A small green flag next to the dial drops when the device is armed, which can be seen through a transparent window on the front of the timer. Unlike most time switches the CD-14 does not reset itself after it is activated, and resetting the timer is a unusually difficult task, requiring the timer to be partially dismantled and the dial removed. The movement in the CD-14 is very elaborate, and is built around a mechanical spring driven lever escapement movement. The movement is electrically wound by a 12 volt open frame motor in the bottom of the device, which is triggered automatically whenever mainspring power drops below a certain level. Sangamo is well known for the quality it lavishes on its timepieces and the CD-14 is no exception; most of the internal parts have been milled, and nearly every gear in the movement is covered in gold plating.

There are a lot of unanswered questions about this device, not the least of which is why Sangamo produced a countdown timer that seems purpose built for the mad scientist doomsday weapon market. The cloth cord attached to the device is terminated by a threaded cannon connector, which strongly suggests the CD-14 was built under contract for the US military, but is hard to imagine a use case that would require s single shot timer throwing a switch 6 months in the future. The level of manufacturing excess in its construction suggests that , whatever the CT-14's intended use is, its builders were very anxious that it not fail to operate at it's appointed time.

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This bizarre and hard-to-find device is a purely mechanical illuminated display, which utilizes a series of slides to block light and display numbers. Each digit consists of an X and Y axis slide: the X axis slide contains all of the segment patterns needed to display numbers using the four vertical segments, and the Y axis slide contains all of the patterns needed to display numbers with the three horizontal segments. A series of cams move the slides in lock-step, opening and closing the slots in the front of the device as needed to display numbers. This display is a fully contained clock module, and includes a synchronous motor and alarm mechanism that closes a set of contacts when the alarm is tripped. Four knobs below the display allow setting of the time and alarm, as well as activation and deactivation of the alarm and manual closure of the alarm contacts.

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The A-11 is one of the most common styles of aircraft clock in the world, and the clock pictured here, manufactured by Wakmann, is a fairly representative example. A-11 form factor clocks are basic, time only devices with three hands and a winding and setting stem located in the lower corner of the face. A threaded plug on the back of the case can be removed to gain access to the regulator lever without dismantling the entire clock. Most have a standard 12 hour dial, though 24 hour dials, such as shown here, are also sometimes used. This clock contains a 7 jewel movement manufactured by Revue Thommen, a newer movement that saw use in many different models of aircraft clocks. The example shown here was manufactured in October of 1977.

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