Unfortunately, I can't enlarge the picture, as Vodacom is on a go-slow in my area. So this may be a little uninformed... Musgrave used the OB prefix on any loose barrel or barrel blank they sold to the trade, except if a specific serial was requested. So there are many rifles of various types and configuration out there with OBxxxxx serial numbers. The safety on a Santa Barbara action sits on the trigger housing, and the lever sticks out on the RH side of the rear action ring. If the trigger is replaced, the safety lever will be gone. The current Zastava actions are almost identical. In fact, they are rumoured to be made on the same machinery that the original FN Mauser and later Santa Barbara actions were made on. There is not really such a thing as a Mauser mod 1908 action. Maybe a 1898? That is what the Santa Barbara was based on, with quite a few improvements. If the stock was made by Musgrave, as it seems to be from the pic, it should be made from Turkish walnut. Barrel life depends on a lot of things, primarily the round count, but also a few other, less accountabe factors. Often, a worn barrel can be set back a little and rechambered to extract a few thousand more accurate shots.