I'm pretty sure Seapora is just the private label brand for aquarium product distributor Royal Aquatic. Royal Aquatic is the USA wholesale distribution arm of Big Al's pet, and the only remaining division of the company that I'm aware of. My assumption has always been that Aquarium Industrial/Aquarium Masters/AI Incorporated (one company, multiple names) is the manufacturer based in California, although they import a bunch of product from other countries (I believe this is primarily raw material). I think "AI" manufacturers tank for both their brand "Aquarium Masters" and other brands (Deep Blue and Seapora). That being said I don't know who owned Deep Blue, but they are seemingly gone, although they could've just been owned by "AI" or Royal Aquatic.
My assumption is that a Deep Blue, Aquarium Masters, and Seapora tank are all identical from the same factory.