I have come into possession of some of my grandfathers things including some aircraft parts that he had. He was a naval pilot who flew single engine fighters in WW2 and then at some point transitioned to flying helicopters (some sort of sikorsky) which he piloted in the korean war. After he retired from the navy he continued to fly as a civilian contractor for the air force until around the 1960s. I imagine this came from one of those aircraft.

This appears to be a clock. The knob on the bottom left winds it and it will still operate but barely and only when sitting almost perfectly upright. Turning the wind knob to its limit doesn't even last 24 hours though which I suppose would be perfectly acceptable for a flight operation. The knob on the bottom right switches the day/night indicator. I am not sure what the "stop/go" switch does.

I have a few questions about this clock if that is allowed:

  1. What aircraft is it from?
  2. Since it can be wound mechanically what is the purpose of the plug on the back?
  3. What does the "stop/go" switch do?

Clock Front Clock Rear

  • $\begingroup$ If you are able to move the stop/go selector to another position I suspect that there is a "0" behind it. Based on the description in the answer that you received the 0 position is used to reset the clock, which is done by pressing the button in the lower right. In the catalog photo this button is marked "Push Hard". In your photo the button is unmarked, perhaps due to years of being pushed hard, assuming that the button performed the same function as the other clocks. $\endgroup$ Dec 18, 2023 at 4:50
  • $\begingroup$ @StevePemberton: Possibly but that little circular window at the bottom has an indicator that is either white, half white half black, black, or half black half white. I'm assuming to indicate day, evening, night, dawn. Pressing the button in the bottom right seems to only change this indicator. The clock also runs when on stop, 0, or go. $\endgroup$
    – jesse_b
    Dec 18, 2023 at 11:39

1 Answer 1


Here's an excerpt from page 13 of the manufacturer's 1966 catalog for a very similar clock, model 651-12-24.

catalog page

  1. It might have been installed in many aircraft. Logos on page 14 include American Air Lines, KLM, Cessna, Piper, United Air Lines, BOAC, USN, Lockheed, Beechcraft, PAA, Douglas, and USAF.

  2. The manufacturer's catalog mentions "bulbs-5 volt filament / standard connectors-to customer's specification," so the plug on the back must be for its lightbulb(s). (This is also from page 13, just above the excerpt.) The connector is like the 3-pin XLR sometimes still used for lighting, e.g. Littlite goosenecks for audio mixing consoles, but its pins are spaced differently.

  3. When the stop/go switch points at stop, the clock does not run. When it points at go, the clock runs. The excerpt's description begins: "Operation: Start, stop, ...". So it's not intended to synchronize to your wristwatch; it's more like a stopwatch, which happens to be able to measure durations of many hours.


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