Looking at the rim of my sons similar sized tank, I would say that the trim/ middle brace has definitely been removed. By the looks of the “cut”, it’s shaped like the center brace too. Also it happens to look like it lines up directly over the center brace along the bottom brace.
For what used tanks normally sell for I would pass. However you could order a replacement trim assembly as well. For a 90/100 gallon tank I would think you could find many more used ones in that price range. If the tank for sale included other equipment, a nice stand, etc... I may would purchase to get the other equipment and stand and trash the glass tank (could keep the tank and buy a bearded dragon or similar tho!?). In my area, somewhat rural NC, I could find a nice used 90/100 gallon tank within a month no problem.
Did you get the dimensions? Looks like it could be a 90- 48”x18” or a 120- 48”x24”. As long as the footprint is the same you have the option of a couple different ”gallon tank sizes” since most common 90 gallon tanks have the same footprint as common 75s the stand and other equipment should work fine for both. Either way I would feel kinda sketchy about filling with water and lots of money with the missing brace.
