Might seem a bit out there, but color matched paint is so easy these days. Even if it’s faded, they can match that. You could just touch up the worn areas and try to leave as much original as you wanted. I’m kind of a traditionalists with old mechanical things though, so maybe this is bananas.
Yeah, the lighter areas are where it has come up and been reapplied. Linseed oil gets darker with age, but I think the really dark areas are from a mold or mildew. I’ve only seen that in places with a lot of moisture year round.
For what it's worth, I've got a silca from the early 80s and an SKS (I believe) from the 90s. I can still get parts for both.