Concerns About Counterfeits. General Question First

If you have a slabbed coin, and you have reason to doubt it, then
the slab needs investigation, because it follows that the coin inside may not be authentic as well.
In this sort of situation, it is logical that the slab must be authenticated before any consideration is given to break the coin out.

I must admit: I have far better access to the facilities to authenticate a coin than I do for slabs, and for me, that is one of the reasons why I prefer raw coins. A coin inside a slab cannot be investigated, and thus, the slab has to be destroyed for that to happen.

There are other members here within the CCF that can provide good advice on how to authenticate slabs, and perhaps avoid having to break the coin out.

Nevertheless if you eventually prove for yourself that the slab, is, in fact genuine,
I see very little need to destroy a slab, unless you are aiming for a higher grade, with a re submission, and that should have nothing to do with the authenticity of the coin.

If the coins you are talking about are not worth the cost of a professional opinion, then they are probably not the sort of coins that attract counterfeiters. I would say you are 99.9%+ likely to have good coins.

Another suggestion, in the future if you are looking to buy a coin look for ones in NGC holders because unlike PCGS for the past 20 years or more NGC has photographed every coin they have slabbed and posted the images on their certificate verification site. That allows you to compare the coin in the slab with the coin in the image to make sure it's the same one. PCGS has only posted a very small number of the coins they have slabbed.