I just bought the original 313s rims off a guy with a 335is and have the exact-same situation as the original poster:
- 1 wheels is stamped BBS (made in Germany)
- 3 wheels are not stamped BBS (made in Italy)
I didn't realize the different stamps until I got home and thought I ended up accidentally overpaying for a set of reps; however, the stamps inside my 3 wheels match exactly to the image posted by chris_s1. I'm not sure why BMW did this, but I'm convinced that they're authentic wheels