I have two comments. The "U" number on your SMP pistol appears similar to ones that were put on pistols for which concealed weapons licenses were issued in Shanghai. In at least a couple of cases SMP .380s were given (issued) for important foreigners living in the Concession. It is possible that is one that was given to an important personage, who was then issued a concealed carry license for it. Some SMP M1908 pistols may have made points to come into the USA by having an extended barrel put in them. Once in the USA these barrels were replaced by the proper barrel. I bought one of these pistols once that had the extended barrel still.