You can get the hole liners, as fitted to later Gottlieb games, from PBR. They can be trimmed to make them fit the earlier holes, which are a bit smaller. Fit them to sit flush with the play field if you need a square edge, or sit them lower and sand a radius if you need that. Carefully fill & sand the low bit of the pf around the liner, job done. If it was originaly cleared timber finish around the hole, mix some Acrylic in to the filler (I use car body filler) to give the correct colour. If it is a colour finish around the hole, touch the filler in to match. Clear the filled area. The liner will stop any further wear, the cleared filler has not worn on the games I've done this to that need a radius, so it must be hard enough for the job.