aside from VIN numbers (which is probably the most accurate way to tell) look for:
-no side moldings (there should be none)
-the front lip is slightly different (there are many threads on this site that show an itr lip)
-type-r badge on the center console with a serial #
-black suede seats with red stitching
-5 lug of course (unless its a 97 i THINK)
-no sunroofs (unless someone ACTUALLY got one installed - i have yet to see one on an itr)
-paint only comes in phoenix yellow, championship white, or nighthawk black pearl (i dont know why anyone would repaint a type-r)
-carbon fiber around cd player, a/c, etc

thats about all i can think of off the top of my head, and these are stock USDM specs, people may have changed things about them. i would get a good feel for what a stock type-r looks like by just browsing the internet. but the most important aspects would be the 5 lug, the badge, and vin number

good luck! i wish i could be getting one of these beauties