What Am I - Firearms Curiosa?

[Richard G]

Hello,
My guess, and it is only that, is that it might be some form of starting\signaling device. For example, to signal when a race competitor has passed a line so that someone else can start or stop a stopwatch or record a time. I can imagine this being useful in time trials where you cannot get all competitors to start at the same time such as dinghy racing in restricted waters or road racing on narrow lanes. All you would have to do do is tug a lanyard as a competitor goes by as the gun itself could be mounted on something else, like a starting boat or dais.
Regards
Richard