Depends on what is stock... the fuel tank and searpost or the rear fender.....
That rear fender looks to be from the 3TB model... Does it have a rubber-type thing that fits on top of that fender? does the fender have cuts/holes?
The fuel tank paint looks to be the 2001 XT600E but I can't see good enough through that picture...
You should check the CDI box (it's the black magic box that is under the seat and right next to the air filter snorkel!
There are some differences from year to year..
Also, on the right side of the engine casing is the clutch cable there or is it on the left hand side of the engine?
Also, so you can know which year that frame is from, check the VIN number and post it here! I had a Yamaha VIN number "decoder" which I posted here a few months back... one particular digit refers to the fabrication year!