Two other things to try if out are new to the K31.
First, unscrew the buttplate and look for a former possessor's tag. It will have the name of the person, the unit that they were in, and where it was. A lot of Swiss K31's have this tag, which the soldier who had the gun put there.
Second, for a lot of information about curio's and relics and K31's in particular, go to
www.surplusrifleforum.com.
Keep both that and this site bookmarked. Can't go wrong with either!
The Doc is out now.
