Just to add my two cents which can be taken however one wants to..
I own a lot of 1st edition base set cards, all of those with the supposed "Thick" stamp look the exact same. No differences other than sometimes some had darker (more) ink than others. They are very consistently sized always, through the holos and non-holos.
My "Thin" holos.....whole different ball game. It isn't one thin stamp, it's many different stamps when looking at my cards, almost like a spectrum of thinness. Some have a very thin 1, others have an almost thick 1, many are various sizes in between. It gets to the point where it becomes very hard to distinguish between a thick and thin stamp. Many are too close to call.
Personally, I think the original thick stamps are all consistent, which makes me believe that there must have been a time partway through stamping (after all the non-holos were done, and many of the holos) where all of the sudden quality control changed. I don't know if they changed to a different stamp or got lazy or what, but my cards are all over the place after that.
Basically "Thin" doesn't exist to me. There's "Thick" ones for sure, then a crapshoot of other inconsistent holo cards.
I own a lot of 1st edition base set cards, all of those with the supposed "Thick" stamp look the exact same. No differences other than sometimes some had darker (more) ink than others. They are very consistently sized always, through the holos and non-holos.
My "Thin" holos.....whole different ball game. It isn't one thin stamp, it's many different stamps when looking at my cards, almost like a spectrum of thinness. Some have a very thin 1, others have an almost thick 1, many are various sizes in between. It gets to the point where it becomes very hard to distinguish between a thick and thin stamp. Many are too close to call.
Personally, I think the original thick stamps are all consistent, which makes me believe that there must have been a time partway through stamping (after all the non-holos were done, and many of the holos) where all of the sudden quality control changed. I don't know if they changed to a different stamp or got lazy or what, but my cards are all over the place after that.
Basically "Thin" doesn't exist to me. There's "Thick" ones for sure, then a crapshoot of other inconsistent holo cards.