I just bought one of the 1960's versions  But they are all a typical 303 pattern gun.  Mine had all matching numbers on the metalwork, but the stock was a 4 peice mis-match.  All 4 peices were numbered differently and had a different color.  There is a considerable crack in the underside of the forward upper handguard, and top screw of the buttstock spins without biting any wood.  The exposed metal has about 25% blue left, just enough to make it look gray instead of shiny.  Unless you really want one, save your money and buy a better one on an auction site.

It appears I'll have to refinish the metal with black engine paint and buy a new stock set to make it look presentable.

I wish I had bought another K31 instead.