I believe the 29xx and 35xx switches run Real IOS. One way to tell is to go to Cisco's site / CCO and try to download an OS image, if the OS image is like a 12.1.x or a 12.2.x then it's probably Real IOS, and if the version number is < 11.x.y then it's Fake IOS.
Be very careful, most older/cheaper Catalyst switches run Fake IOS.