The fingerprint stain was a little annoying, but the card served as a nice filler at a reasonable cost earlier in my '62T set building. I can't imagine what would have caused it. It seems more like a chemical discoloration than a colored topping. Other than the mysterious fingerprint, the card is in really nice condition.
Here's a page from my '62T binder showing my new Frank Robinson card. Although not as well centered from top-bottom, there's no more fingerprint to look at.
Finding marked checklists from this era of cards is definitely a common occurrence. Somehow, this was my only marked checklist in the '62T set and I was able to find an unmarked checklist for a really good price.
Here's the final page from my '62T Topps set depicting the last 4 checklists, which are all unmarked.