throttle body question

I recently had my TB off my car, and when I was putting it back on I realized that on the back of the TB where the gasket goes that it had "50mm" engraved in it. I was under the impression that the SCs came with 60mm tb stock. I have a '91 5-speed. Is that engraving for something else, or are our TB's only a 50mm?

Brandon
'91 SC 5-speed
P&P heads and intake
Flowmaster force II exhaust
B&M ripper shifter
15.01@90.73 (bone stock times)

There are appaarantly more than one TB for our cars over the years. I have one with no markings, 1 with SC embossed on it and I had one that had 50MM on it. The 50MM was smaller, but I can't remember whitch year that it came from. The others measured at 60MM.

Jeff

I beleave the early cars had 50MM and I think maybe 93 up has 60MM