More history...
At the time "All-Glass Aquarium Co." introduced the all-glass tanks (1969 or so) the leading tanks were "MetaFrame" built of stainless frames and black goo (aquarium sealant) with slate bottoms. They leaked after a few years, the goo squuezed out, and the "Stainless" frames were hard to clean. The All-Glass units were truly revolutionary at the time, and that is why they named their company "All-Glass".
The ability to make aquariums without frames came about as a result of the development by GE of a "space-age" RTV (room temperature vulcanizing) silicone sealant that we now take for granted.
Also at the time, many aquarists were building thier own all-glass tanks using the silicone aquarium sealant. You simply bought the pieces of glass cut to size, taped them together on the outside, and applied sealant to the inside corners.
In fact- this is a way you could get your "all-glass" aquarium- in any size you want. Just be sure to use the right thickness of glass (copy the commercial companies' practices), use real aquarium sealant (not automotive type), and use tempered glass at least on the bottom.
And if you are building a tank 55 gallons or larger- I would use a piece of glass to add a brace across the top, midway down the length of the aquarium. Allow clearance for your top and reflector.
Based on past experience- you will not save any money, but you will be able to build any size you want and have the satisfaction of doing it.