Would you have any idea what the "BS" stands for? I'm sure its not "Buck Stix".

AFAIK these letter codes are Mauser factory internal designations for the barrel steel used, source and lot. F.i. most eaarly Mauser .22 rifles have a "Ch54" steel code marked on their barrels. Sorry, but these barrel steel codes are not documented, so they are unintelligible today.