Viper, et al: As you may be aware, or not, the owners of the coins frequently used nails to make the holes. Not a drill bit, not in this century at any rate, or the last one.
I've seen plugged coins in old ANACS holders with "plugged" on the label. I don't know if they still do this. But no, there was no cutout in the slab itself, or the plug in the slab with the coin missing, of course.
metal inside hole If a nail or a square drill had made the hole how did melt the silver inside the hole? it take 1400 deg to melt silver. and were the hole drill or pounded in it would be smooth like a nail from 1800 would have left. maybe the south back then had a lazier they did not use in the Confederate war?
I don't understand the concern about getting the coin slabbed. It's not a particularly valuable coin and in its condition probably isn't worth much more than $15. It would cost about double that to get it slabbed IF you could find someone to do it. Whoever punched the hole laid it on something solid and flattened the opposite side when the punch went through. Also the coin is distorted where the punch pushed the rim out. There are services that will "repair" a holed or damaged coin but it would many several times any value you would realize from it. That type of repair is usually reserved for truly rare and valuable coins. My advice is to put it on ebay for someone who appreciated things like this and buy yourself an undamaged coin.
I know it had a plug in it when I got in the 80's but it was lost.most likely, in and in 25-29 year about 4 of them moving place to place in the Army. no telling were that plug maybe. when the Army move you they pack really you fast & mess up you things and the movers will steal you blind!! cause they know the government will replace the thing you claim are gone or damaged!