sure fire way to find out is to start drilling, you will know soon enough….chances are pretty good the bottoms the only tempered panel though…
as for calling the manufacturer, seems like wasted time to me…chances are there is someone there who has a list of the glass used used in a particular day, that said, from what i understand of mass pro tanks they tend to use what they have on hand…
i would try the laptop trick , though it isn't 100% it is pretty good..
barring that…wear safety glasses….