Title pretty much says it all. An example of an inverted knob-S mint mark in ANACS MS64 slab 7720502. Purchased for $30 unattributed on
ebay.
I thought for a while that there was some kind of odd doubling or repunch on the S, but with my fancy new microscope setup, I can see that it's just toning and a little hit to the bottom tip of the S.
Note: the zoomed image of the S is upside down, so it's easier to see the knob-S mint mark rightside-up.


