these guys already said it.
Codes- look for BSW. they were only produced for 3 years making them harder to find. alot of people like the Sauer models for their finish is usually really nice.
early war models will usually be nicer.
BORE BORE BORE. i had a beautiful BSW k98, but it had a shitty bore. totally ruined the rifle for me. didnt shoot straight.
make sure the swastikas are not peened off / damaged.
early year rifles ( up to '41 ) "should" have a FLAT buttplate. 41 and later years should have a cupped buttplate. but you will often find that the Russian refurbished rifles have the wrong stocks, missing sight hoods, missing cleaning rods. '41 and later years were cut so the front sight could accept a sight hood- for an RC rifle, just buy a repro sight hood and cleaning rod.
oh yeah, different years had different cleaning rod lengths too.
some of them were counter-bored ( last inch or so of the muzzle was ground out to give the barrel a new "crown" youll see the rifling is smooth / gone there
just make sure the bore is good, has all the markings, stock doesnt have to be pretty but it should have no cracks and a snug fit.
go buy one and post pics!!