Some of my own coins in my possession have displayed this issue of degradation due to the gap the bulge induces on the hologram.
All of my other coins that have the recess in the metal have not displayed this type of degradation.
The specific area this is affected is only in the middle where the paper private key exists which causes the bulge. The outer areas have not in my knowledge had this issue even with these coins.
I've had one such customer ask me about this in the past.
If you are worried about coins being tampered with or not sure of the state of such a coin you could always request that the coins be sent to you while funds are held in an escrow until you are able to physically check for yourself that the coins are indeed not tampered with before releasing payment to the seller.
This is the responsibility of course of any buyer of physical coins to know the possible risks associated with physical funded crypto coins.
Hope this helps.
Thanks for replying and clarifying.
I was just curious as none of my 1st batch coins showed any such degradation. Maybe I have the cold UK weather to thank
Anyways, thanks for the help. Much appreciated as always