what is it

I doesn't look home made, so my guesses would be:

1) a signal that could be activated from inside a casket. In victorian times beople were "deathly afraid" of being buried alive. They would have signals or bells hung on their tombstones with tripwires run down to the casket in case they woke up inside it.

2) a naval sounding device. A lot of harbors required ship sound off before entering. Before big loud horns, they had little cannons to make a big boom when they entered the harbor.

3) a naval signal device. Just a stab in the dark, but you could insert a flare cartrage an have this mounted above the flamibles like flags and sails. I don't know when 12 gauge flares were developed, probably after this thing was made, but a guess.

It would make a great alarm!