Does anyone recognize this label?
 

Sealing up the case of a card. I am guessing it is a shop or early authenticity service maybe?

Sellers have put tamper evident stickers over the openings of top loaders. My guess is that's the case here, though I've never seen it down on a screw down.

yeah, tamper stickers
 

Yeah, that looks like a "tamper proof" sticker that dealers used to put on screw down holders & top loaders. If the seal was broken, then the card had been taken out for whatever reason. That's old school stuff, predates PSA/SGC boom