ahhh ok I get it now. I do have images of the lock but it was way back and they are not good quality, ill send a link anyway but I am there again on Wednesday so ill get some better pictures then.
Also what nipple thread are these? or does it vary between guns?
Here are the images of the lock, like I said, it is pretty dark and not the best images but i will get more:
https://i.imgur.com/gSBYxZo.jpg
https://i.imgur.com/vvfUcoA.jpg
https://i.imgur.com/DICYGOR.jpg
Also as a bonus, here it is on my grandfather wall along with two shotguns:
https://i.imgur.com/Prl4mrs.jpg