Unfortunately, it doesn't look like you'll find much on the frame. Judging by the derailer hanger it was a better quality bike. The lower-end models generally have plain dropouts and use adapter claws. You could weigh it. That would give some indication to the quality.

Despite what others have said, I bet you'll be able to fit a 700c wheel in. A skinny 700 tire is about the same diameter as a fat MTB tire. But of course the only way to know for sure is to try it.