Looks like about everythings been covered on your Underwood. Sorry about the gas cylinder issue. It's not something you see on carbine barrels a lot, but they are out there. The rear sight is also unfortunate, but not a s bad as the barrel issue. I have seen more than a few Bavarian carbines that had the rear flip sight messed with. This is one of the first though where the sight was put in backwards. BTW, have you found any additional Bavarian markings, if it is one? If you are going to sell or part it I'd be intrested in a few things, mainly the stock if it's as nice as your pictures depict. Let me know, thanks.