While cruising the spectacular swap meet at Super Chevy Memphis, I spotted this on a table...
The tag reads "M22 '69 Model, 09-18-69, Fresh Build Like New"
Problem is, this ISN'T an M22. The dead giveaway is the input shaft. Notice the coarse splines? All M22s were built with fine spline input shafts as part of their heavy duty assembly. The coarse spline shafts were used only on the M20 and M21 transmissions.
I won't speculate on if this was just an honest mistake by the seller, or an attempt at screwing someone over. But this points out why it's always good to have some knowledge and info when you're walking through a swap meet looking for parts, and maybe that next hidden jewel for your collection.