Without a manufacturer stamp/engraving, the origin of this trumpet is near impossible to determine. There are clues, however.
Why would a company not identify itself in some way on its product? Barring prototype status, the likely answer is that they don't want to be associated with the product.
Some of the details, or lack thereof, reveal a simplicity in their use, such as basic water keys and a lack of a third slide stop, in addition to the lack of engraving on the bell, which tend to indicate a TSO (Trumpet Shaped Object), typical of build-to-a-price instruments made in China. That this trumpet is in a rudimentary budget case is another clue.
It's interesting that the previous owner used it throughout college. Does it function as it should? In what condition are the valves? How does it play?