Not sure about the newer ones but I know for sure that the ones from the '70s are VERY well sealed, I tried cracking one open and it was quite a chore... there was an impaired proof in there that I wanted to get out.
I received the 2021 silver set a couple weeks ago and I have no idea how someone would open it without visible damage on the case. There's nothing to grab onto in order to break it open.
I think the seam is along the top in your second edge-on photo. I just grabbed a 1999 silver quarter set that was nearby and tried prying it open with my thumbnail. No luck on that one. I may well be mistaken. I'll try to find some more later and see how many of them I can open.
Yup, you're right @-jeffB, looking closely at it that is the seam. Hmm... maybe wedging an exacto knife or razorblade in there. Still might be visible that it was done, though.
Yeah, I'm not sure I want to vandalize any sets, but I would've sworn I'd pried a few apart with ease. Now to see whether those were the exception.
I suppose the approach then is to find a way to get purchase at that seam. My photo makes it look like there's an indent in the edge where you could grab the seam, but it's solid clear plastic up the side of the case. My fingernails were not up to the task of trying to catch the seam...