Bigger than it looks in the photo. 36 x 18 x 18 would make it a 40g breeder tank. Much bigger than what I took it for, I'd not trust it without a frame.
Reef Savvy is a top quality manufacturer. Most makers don't come close to their quality. This one appears to have had a plastic rim, like you'd find on most any generic tank, around the top and bottom. Aqueon, Marineland, or Deep Blue most likely.
You might be able to get a new frame from one of those makers, but I'd doubt it. 40 breeder is a common size, you might find a broken one locally that you can steal a frame from. Place called 'Over the Edge' makes replacement frames. They're the only ones I know of, reasonable, but not cheap.
On a tank that big, I'd definitely replace the frame before filling it. A popped seam is a huge mess, just wouldn't be worth the risk to me.