USAAF/USN used AN5741-1 / 37500 aircraft clock. 8-day aircraft cockpit chronograph clock manufactured by The Elgin National Clock Co. It has a black bakelite case and measures approximately 8cm in diameter x 4cm deep (excluding winding/adjustment knobs). The black 24-hour dial incorporates a further four subsidiary dials recording seconds, minutes, elapsed time (up to 12 hours) and date. Rather than using radium, both the main 24 hour numbers and hands were applied using a fluorescent luminescence paint that is activated under UV light. Winding and setting of the hands are done using the knob at the lower left of the case. The centre of this knob has an integral spring loaded button that can be used to change a small coloured circle within the elapsed time dial from white to red. There is also a very small 'SET DATE' push button that advances the date dial by one day for each successive depression. The knob at the upper right side of the case is used to operate the chronograph features. Pressing it once stops the main seconds hand while the clock continues to tick (& the subsidiary seconds hand continues to tick). Pressing the knob again resets both the main seconds and subsidiary seconds dial. A third press restarts the seconds hand and subsidiary seconds dial.
The rear of the case is marked 'AN 5741-1, Mfrs. Part No. E-37500, Contact NXs 1301, Mfrs. Ser. No. 001733. Elgin National Watch Co.' Adustment to the movement can be made at the rear. An impressive looking scarce clock in very good used condition. It ticks strongly, all the dials function and it appears to be keeping good time. It came to us with a custom made wooden solid mahogany stand and chromed bezel. An excellent display piece. Stock code C27466.
The back of the bakelite housing is stamped in white paint with H 88 - C - 573 - 11, and still has the complete manufacturers information molded into the bakelite:
1) They added a second mainspring.
2) They changed the winding system.
3) They fixed a setting problem with the Chronoflite that caused teeth to wear rapidly.
4) They redesigned the civil date mechanism so that the pin that changes the date would not break or bend when being set counterclockwise.
The last mechanism was patented by Hamilton engineer Francis Meyer and granted on October 10th, 1944, as patent #2,360,305