Funny that I'm going to respond to myself. I've spent a while trying to find the answer to this, but I think I've found the answer. Please let me know if I'm not correct, but the "stamp" is actually a sticker. I thought it was engraved/stamped into the horizontal support bar. That being said, there are other differences to tell whether it is a RB303 tonearm. The RB303 has a smooth taper coming off the pivot point to the tonearm and the numbers for the VTF are not imprinted with white on the RB303. What I don't know though, is whether other Rega tonearms have the same characteristics as the RB303 I found above. If anyone knows the answer to that question, please let me know. Thank you.