double checking to make sure this thread isnt mac specific
Yes, if a prototype was produced in sample sizes of more than 1 or 2 units, chances are there's a number of them out in the wild. I'm a collector of prototype Apple Watch bands specifically, so while I can't speak to the distribution of macs, I can say there are some bands I have that were very rare small scale unreleased designs which most certainly weren't made to be seen by external collectors.
Just all depends on how many were produced, if any.