Probably "Ultra Products" (from TigerDirect). They had some cases that had a similar front bezel to those Chenming, etc., cases. Very similar, probably same OEM.
I got the smaller version of this case free after rebate more than once. Sometimes from TD and sometimes from Fry's Electronics.
I just found a purple one at the dump. It is Thermaltake branded. It weighs a TON!
A lot of Case manufacturing specially back then was like this. I don't know who designed it, the Chieftec versions really didn't hit until well after the Antec versions did but they were cheaper and the exact same case so the Chieftec versions became the most popular. But several other companies had a version of this in their portfolio. But people forget that companies have to work their way from the ground up and often use third party manufacturers till they get more vertical. I don't know what Antec's manufacturing strength was back then, I don't know if Antec developed and had to license it to Chieftec to get their manufacturing (and then Chieftec then let others rebrand it), or if Antec commissioned the design with an expiration on exclusive rights, or if Antec simply got into the Chieftec factory saw the case and asked Chieftec for their first few runs. So I wouldn't assume right out of the gate that Antec just re-branded someone else's case.
I think the point of newer cases is that it's a lot more of just a frame and little to no structural support outside the fram. For example on Fractal one of the strongest built enthusiast cases the whole center area at the top are plastic plates to hide sound deadening material, where these old Antec's/Chieftec's the top was like 6mm thick steel riveted to the frame. The doors on these cases where nearly as heavy as most cases empty are today.
