Odd Percussion or Cartridge Firing Lock

[Gspragge]

I came across this today. Heavy brass construction. The numeral 2 on parts of it,
no other markings visible. It would drop into the top of the body and be held by a spring
clip at the front from the looks of it. I have the top plate loose and am soaking it in diesel
fuel to loosen and clean it out. Appears to function with a linkage or lanyard.
I have no idea what it is out of. Large swivel / fortress gun, Harpoon cannon ?
about 6 1/2" in length.

 

[Gspragge]

It cleaned up well and functions properly now
as it was rather gummed up with grunge etc.
I found no markings other than the screw holes are
numbered.

 

[Gspragge]

It seems most likely that it is from a swivel bow mounted Harpoon gun of unknown
maker last half 19th century. It is very similar to these examples.