Hi damon. that is not unusual. There is a good and bad side to it. I bought a lot of 10-12 nos pf's from a guy, a while back, and he cleared them all with oil based poly in the 1990's. they were all late 1970's ballys, like globetrotters, ek, matta hari, and ever an paragon and charlies angels. the good thing is 90% of the pf's I buy and that are shipped to me from the 70's have serious, to real serious cracking in the art and finish due to expansion and contraction, right on the grain. To me that cracking is really ugly, and many many pf's I end up repainting all of the effected areas. The bad is oil based anything has a golden tint to it. The good thing is they have no cracking at all and look new, just a bit golden.
\Now to answer your question. I wish I had a pic of a before and after, but I only have before pics of the 2 I have left which are CA and EK.
Every pf I get, the first thing I do is sand off the finish down till I start hitting ink. so by removing the bulk of the clear, I get rid of the color you are looking thru, but not the stuff that is right on the surface of the ink, and soaked in the wood. I think it is the linseed oil. So to quantify, I would say by sanding it off till right before you hit the paint, you get rid of 40% of the shade on the painted area, but not the bare wood area.
Here is the way I feel about it and what I would do. but first let me mention what happens when you install a nos evil kenival that not only had the cracking along the wood grain, but was alligatoring a bit, after all it is 40 years old and was prob stored in a wherehouse. The point is, the paint was literally falling off up at the arch and heavy wear areas in 6 months of play. Its like it aged right before your eyes. It looked bad and got worse with every ball. If it wasn't populated, it would have been clearcoated by me, and the finish would have been locked up, and stable.
Back to what I think about it. I am 50/50 on the 2 ways to deal with it. The first is to leave it as is, but to wet sand, and buff polish, just because most of them are not, and at least you can make it super smooth and glossy, and since the game is 40 years old, it really dosent look out of place. Looks like a survivor with a perfect pf (a survivor is a unrestored, but all original, cherry car, so I guess it applies to pins also) the other way is sand it off and have a proper clear put down that is sanded level, and polished after. either way looks awesome, just different than reproductions.
final word of what turned out to be a novel, is I would rather have a old nos pf cleared with poly, than a uncleared nos pf that needed 30-40 hours of paint before clearing. that is some serious money, and it happens ALL THE TIME!!! when you buy a nos pf and the person sends a nic pic from 4 ft that shows the whole or half the pf, you cant see the cracks (this happens to me so frickin often by bastard sellers) and they are not mentioned when you ask about the condition. so lets say you just spent 600 on a nos pf with ship and when it gets to you it is cracked up real good, and you ship it to mr reputable clearcoat, he is going to say if we just clear this it will look like cleared crap, and will magnify the flaws. the inserts have to be leveled, which means all of the insert key lines have to be painted, and we should repaint, at least the bright colors, and the black, where it shows the most. say a 400 dollar budget for leveling/painting inserts and painting the cracked areas that are the most visable, plus 400 for the clear coat, you are now up to 1400, plus shipping, cant forget that.
then again, once it is done, the machine is worth at least as much as you put in to it. I have never seen a restoration not sell for what was spent on the parts (assuming it is done well, and the rest of the parts match the pf). and you would only sell it if you had to, like for a roof on the house,
and pinball is an expensive hobby.
though I used to build 1/4 mile drag cars cars, and every weekend I would spend between 500-1000 on parts,fees, and travel or should I say for the weekend. MY final car was a 66 chevelle with a 502 professional built motor, and a 4k black with flames paint job (this was 1994). I spent WELL over 25k on that car and sold it for 10k.
My other hobby was women, and the return is even worse than hot rods!!