Help ID, JP Sauer and Sohn double ?

[roklok]

I won on Gunbroker this German double 16 gauge I am positive has at least some connection to JP Sauer and Sohn, likely built by them but unbranded. It was listed on Gunbroker as a "Spanish 16 gauge", I won the auction for $272.00. I knew it was a German shotgun of some sort. When I received it and examined markings and features, it certainly appears to be a Sauer shotgun. Curiosly though it is completely unbranded except for S&S stamped on underside of barrels. My understanding is this indicates Sauer and Sohn. There are also various German proof marks on frame water table and underside of barrels. It is equipped with cocking indicator pins, a horn buttplate, germanic cheekpiece, and sling swivels. A really nice handling shotgun that weighs 6 pounds 1 ounce with 29.5 inch barrels. Any ideas exactly what I have ? It certainly appears to be a Sauer shotgun, just really strange it has no markings visible when assembled. In fact the only visible markings when closed is "nitro" on each barrel just above the frame.