So we bought a used tank, guy said 135. I haven’t measured it. It leaked and when I got it home I started disassembling it. Popped of the bottom piece and it was 1/4”. The rest of the tank is 3/8. Is this normal?
Google how to do a polarized light test for tempered glass. If the bottom is tempered glass I would expect it is original. If it isn't tempered I would expect it is a replacement.
Tempered glass is stronger than non-tempered so it is possible that the bottom is thinner. It is hard to get a sheet of tempered glass the correct size. It would be very easy to get a sheet of non-tempered glass cut to the right size. I used to be able to get 1/4" glass cut at the local hardware store. They definitely never carried 3/8" glass though. Weaker thinner glass on the bottom doesn't make any sense.