I just bought an original Macintosh and the mouse is not normal in one way; it has the cable and connector from a LISA mouse. I've asked for more and better photos of the mouse/serial labels etc. from the seller prior to them shipping it to me but for now I just have the attached images. I've also added a LISA connector image for comparison.
Sadly it was a donation and I can't ask any questions of the original owner.
My guess is that the mouse had the cord replaced at some point and given the rarity of the LISA cannot understand why this was the replacement used. I'll open the mouse up when I have it and see what's inside.
Maybe the build date is in 1983 and it's something special like my week 2 1983 keyboard.
Using a Lisa mouse cable could make sense given the time period in which the repair was likely performed -- the Lisa didn't sell well, and after the Mac started to take off they'd be considered of low value. Sure, we consider Lisas quite valuable now, but "retrocomputing" didn't exist back then, and by the end of the 80s they were just considered obsolete junk. If the mouse was headed to the trash anyway, might as well scavenge a usable part from it.
Anything is possible. It would cretainly have been nice to speak with the person who owned it first.
Any Lisa part would still have been rare and it is an odd thing I've never seen in thirty years of collecting computers.
Just looked at my Lisa mouse. The cable stress relief is the same as on the apple II mice so someone could have swapped in a cable from a broken Lisa mouse (Lisa Mice are NOT ergonomic or a pleasure to use afterall).