How do you tell original hood latches?

[foxfire42]

I'll be at a swap meet this weekend. I would like to know how to tell an original hood latch specifically 1931 if there's a difference in '30 and '31. I've done a search but most threads were how to restore latches.

I've always thought the repro latches had a smaller diameter shaft whereas the originals were noticeably larger. There has to be other differences that I'm missing. Up til now I've only looked for the thicker shaft and 2 tabs rather than 3 to fasten them down.

Thanks in advance