If you can still make out the marks try putting a mark there with a fine tip red permanent marker . Does that advancer work smoothly ?
If the springs have been corroded they will be weak . This will cause advance to come in early . When you get it running observe the advancer with a timing light and keep track of when it reaches full advance . Check this against factory specs . A k0 would begin to advance just off idle and be all in by 2300-2500 Rpm .