That's interesting. One gun I recently bought used, I can't remember which one, but the one kid was trying to read the serial in the yoke and an older guy said use this one, it's easier to see, referring to the one on the butt. That would've been interesting if they were different.
So, OP, I take it for granted that your paperwork from the original sale to you has the yoke number on it? Interested to hear what S&W has to say about it.