A real fun gun, I have the 600 and 677 .177 version. The main faults you may find are gas leaks and a floppy shuttle which are both easy fixes. The shuttle can be loose due to the cam ring being worn, it has a square aperture that can get rounded. You can get new cam rings or adjust the square cam bar to compensate. First thing to check on the shuttle if it is lose is the two allen grub screws that secure it. The body is made from Mazak/Zamak and can be painted or polished to the silver metal finish. A few people like gingernut have the rare nickel plated finish one. They are not over powerful, just sound like they are. There is not much on them you cannot repair. Don't buy one without the back sight unless you get it cheap.
Baz
BE AN INDEPENDENT THINKER, DON'T FOLLOW THE CROWD