How do I know If I bought a Sealy Mattress?

I bought a mattress from a older gentlemen from craigslist. He said the mattress was a sealy from the ST Agusta collection. There is a tag on it that states st agusta but no where on the mattress does it say “Sealy”Im just curious to know if it really is a Sealy. . .Does anyone know if Sealy made a collection called ST Agusta. The Warranty tag along with all other tags are gone except smalll paper tag attached at the side of the mattress and it says ST agusta. . ..