You have a Belgium made gun as indicated by the ELG in the oval. And it is 12ga indicated by the 12 c in a diamond. The other marks are typical proof marks and the 18.2 is the barrels interior dimension in millimeters I believe. If I were trying to fix this gun I would look for a similar Belgium made one and scavenge the parts from it. There are quite a number of these old Belgiums floating around out there and they are mostly of dubious quality. I doubt the gun has significant value aside from sentimental value to you and your father (which can be a considerable value.) But investing in a skilled gunsmith to make the parts to bring it back to shootable condition probably wouldn't make much sense.
Since you didn't cite any nitro proof marks on the gun and it is prior to era when smokeless powder was prevalent, to safely shoot the gun I would suggest some black powder shells be loaded up for it if you get that far. Black powder shell are available from some custom loaders or you can easily enough load them yourself with a little instruction.
Last edited by Jerry V Lape; 06/01/10 12:09 AM.