By no means the same but it looks very much like a "gun fire arc" limiter thing I once saw inside a ships gun turret, the fellow showing us around if I remember correctly said it was to prevent self inflicted damage in the event that the automatic interupter systems failed, however if memory serves me right it was a bloody great brass thingy with similar markings on it, but it was long ago and the ship {boat?} had been laid up since the end of the war.