As far as I recall, the Wehrmacht gave orders pre-WW2 for rifle stocks to be maintained with lackierend liensemenol - "lacquering linseed oil" - I believe this roughly equates to boiled linseed oil, or a Danish Oil equivalent (not the modern garbage with polyurethane etc in it, but the real stuff). This eventually changed, as linseed became less and less available, to Ballistol (in German use for decades prior to WW2).
So, technically, you COULD "rejuventate" a pre-WW2 stock with linseed (as the pre-war stocks show definite tell tale signs of linseed polymerised finishes), but if the stock does NOT need it, DON'T! I will clean down a dirty original stock with either Ballistol or even Bill Reed's old chestnut of vaseline wipe down on a towel. I no longer chase any laminate, so will defer the preservation of same to others, as, simply, I am sure my info would be wrong on laminates, though pre-WW2 laminates probably were treated as above (again, they show many indications of such treatment). Some people (AHEM! LOL) used to use Howards Feed N Wax, but I see this has gone by the way side, thankfully. It does work well, but it also adds another layer of something the Germans didn't use, and it does darken laminates. I am happy to use it on my Mauser Mm-410B .22 commercial rifle, but NOT on a military rifle.
German stocks seem to have used something akin to vaseline or a quite waxy grease as the stock sealer INSIDE the channel etc and to keep out water along the edges. Swedish stocks DEFINITELY did. I have encountered it MANY MANY times in German original stocks, Norwegian regurgitations and even RC stocks. The Sauer stock I gave a going over recently was chock full of a petroleum based grease inside the barrel channel and action area, that was a distinct reddish colour - possibly axle grease! Whenever I restore a rifle with a Norwegian take-off, I always put in vaseline along the wood-metal interface gaps prior to re-assembly.