I stumbled across this and was curious. I am guessing it is a dash mounted marine clock, but wondered if anybody had an idea. Interesting configuration.
The plug is a clue. The dial is not lighted. The plug appears to be leads of a switch that is triggered for four seconds each time the hand crosses a wire in its path. The duration of the power seems to be controlled by a regulation screw on the case. Could it be a trigger switch for an aerial camera, or a film advance for a similar system? Could possible be a timing switch for some process equipment? More interesting. Any other ideas?
If it was a timer for a plane mounted camera why does it need regulation? What’s the regulation knob attaches to?
If it needs regulation there must be a requirement for some sort of accuracy. I don't know how a bubble sextant works but I've seen them with a clock on the front. On this, the clock rotates in the case which has an index marker, maybe providing a start or end like a dive bezel. If the wire is a trigger it would give you 12 or so seconds to do something, like take a star shot. Or maybe it's a time delay fuze for a mine or a bomb. Edit: This is a bubble sextant, I think that a clock on the front.