^
chances are, your tanks were older Oceanic tanks, that is how they used to make them.
as far as the question of why the trim on the tank that landmineyouth is looking at buying was removed, it may have been to accomidate a reptile screen lid, as is often used on reptile enclosures, assuming that the suggestion of a former life as a reptile tank is true.
as far as glass thickness goes, the only way to know is to measure it. if its 1/2", its not thick enough without bracing for a tank that tall and wide.
if its thicker, its probably fine.
again, I am just going by the building standards that were used pre 1995 when bracing was not often used.
on braceless tanks in the early to mid 90s, even only a 90g was made with 1/2" thick glass.
chances are, if this was not necessary tank manufacturers back then would have used thinner glass for sure.
if we have a 300g only made with 1/2" glass and its also braceless, its not going to hold water for an indefinite amount of time.
landmineyouth, I would consult the DIY board for advice on adding trim/bracing, resealing the tank etc.
good luck and enjoy your new tank!
