Peter, can you show pictures of the breeches open and maybe a picture from the rear of each gun looking down the barrel/s? Also what is your opinion of the current mountings; display, or functional?
The larger cannon looks like it was cut from a gunwale which would be a reasonable way to mount a gun of this size. The only thing that puzzles me is how the gun was elevated or depressed.
Thanks.
37mm
https://en.wikipedia.org/wiki/37_mm_gun_M3
https://en.wikipedia.org/wiki/Nordenfelt_gun