That's a model 17. If you pull the barrels, you can find the model number and the serial number stamped on the watertable.
You are aware, aren't you, that the gun is chambered for 2 9/16" shells - not the modern 2 3/4"? The modern shells will fit, but because they are shorter they will not open up completely when fired. edit: lemme re-write that sentence. Because the chambers are shorter, the shells will not open up completely. Using the same pronoun too many times in a sentence can be confusing. end edit.
Because of this, instead of the shot going down a .663 hole in the end of the shell, it is going down about a .550 hole. This increases pressures and recoil dramatically.
You have three options, shooting a short-chambered gun.
1) find the correct shells (or load them yourself) You can get them here, but they are not cheap. http://www.ballisticproducts.com/pro...er=G1625GHF286
2) have the chambers lengthened. A good shotgun smith should be able to do that, fairly cheaply. You can buy the reamers and do it yourself, but the reamers and measuring gauges you will need will run you over a hundred bucks.
3) shoot 2 3/4" shells in it, putting up with the excessive recoil, until it comes apart on you, one day.
I chose option one, and make short shells.
Meddle not in the affairs of dragons, for thou art crunchy, and taste good with catsup - George of Lod, Year of Our Lord 297
I always take precautions.
Beware the Evil Bullet Fairies.