Ron:
Regarding German gunmaking knowledge, for now I don't think I can hardly live up to your expectations but I'm working on it. I would look for a fine hairline crack at the head of the stock. I don't think a craftsman would go to that much effort without there being a reason. To my knowledge, there wasn't any stock reinforcement on the Simson/BSW or Sauer longarms. It seems that Simson sourced the bulk of their tubes from Sauer. But when warranted like on combos, Pigeon guns and DRs one will see the pipe, 1/2 pipe, or massivem Hakenstück side frame reinforcement. The Sauer combo fell out of favor in the early 1920s but could be purchased thru special order, which seem to have a longer length from the standing breech to the hinge pin. What's your length 50mm??I'd first guess the failure of the stock was due to some dynamics of the cape as others including combos are found with similar pins:
http://www.gunsinternational.com/Sauer-12-gauge.cfm?gun_id=100123186

http://www.crosnoeguns.com/itemdetail.asp?ID=5008

But then again it could be a result of a steady diet of higher pressure scattergun cartridges. Yours maybe be a Simson Modell Astora or Modell 35B. I assume BSW kept the same models. I'd say that Simson concentrated more on auto, bicycles, household utilities and military orders more than sporting versions. Now they could have forged components but I'd say economics forced them to source tubes as well as frames. About the time your example was made there was some friction between Simson and the Association of Zella-Mehlis Weapons Manufactures led by Fritz Walther, so I'd say they didn't source many of the craftsmen of Zella-Mehlis. Suhl also had such an association and it looks as if these ties along with family lines allowed for heavy sourcing between members. I'm fairly sure Simson wasn't a memeber of the Suhl Weapons Manufactures Association.

Kind Regards,

Raimey
rse