Any ideas on this?

[SunnySlopes]

it has S.S.S. & Co engraved on the barrel which someone told me probably means its a Sauer and Sohn of some description (german manufacturer) although i have found no reference to this exact gun code. As for serial numbers ... it has a 197 stamped on the barrel breach end. Other than that it has has ST PR 18 28/53 stamped in dots on the barrel too - which i think means its an 18 bore.

 

[longrifle346]

I know it would fit in nicely with the ones on my gunrack....

 

[Busyhands94]

Maybe 28/53 means it's 28 guage and also .53 caliber. Although a true 28 guage would be .54 caliber. Now go kill some critters with it, small and large!

 

[mykeal]

A true 28 gauge is actually .550" inches in diameter unchoked; there are 28.03 pure lead balls of .550 diameter in one pound. It takes 29.6 .540 diameter pure lead balls to equal one pound.

 

[ThorinNNY]

An 18 gauge gun would shoot a .637 inch ball.Lee makes a .600 mould.Use of a .018 patch should work .018 + .600+ .018 =.636. Lee #90974 mould.
Lyman also makes a .600 mould. LY2645600.

Use a caliper & measure muzzle diameter. It might measure slightly larger than
.637 due to muzzle wear caused by ramrod in loading & cleaning.