Looks to me like Tabatiere action (French or Belgian) with the lock behind hammer and the screw bushing on wrist and hammer screw. Probably “Zulu” shotgun if barrel cut too.
Right it is not a british snyder
Lostinidaho - here is a link to some photos of Snider Rifles
https://www.bing.com/images/search?q...mageBasicHover
As the photos show - the British Snider/Enfield rifles utilized a front action lock
The phot of your lock is of a "back action" lock.As already pointed out, your lock is probably of Belgium manufacture - check it to see if there are any proof marks on it anywhere or markings.
What is the bore size of the barrel? Rifled or smoothbore?
As already pointed out . . this is probably from what was commonly known as a Zulu shot gun - my Dad had one as a kid 100 years ago (no joke).
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |