Originally Posted by Trakhak

Yep. Also, I don't think Trek ever produced an aluminum 520. And none of their aluminum bikes that I remember had discrete-looking steel-ish welds like those in the pictures. Pretty sure Trek's aluminum frames progressed from bonded assembly without visible joining to big obvious stack-of-dimes welds.

In any event, the bike appears to have been repainted, which most bike companies say voids the warranty.

Did the OP buy this bike new? If not, was it already painted when bought from the previous owner? If so, that might be suspicious. And there'd be no warranty, of course.