Wanted to get a call on this -- the auction is closed, but I considered bidding until I started looking at this closer. I think the center design is OK, but the lettering looks strange -- unusually "fat" and lumpy.
Here's what's on
ebay (certified by those [insert adjective plus noun here] at NNC, of course):


Here's a true example sold by Stacks:


These two coins are clearly different dies, at the minimum. I'm not the best at spotting fakes yet, but I want to see if I'm alone in this.
1. Compared to Resplandores, the overdate is supposed to be visible below the "9", and the 9 is supposed to be actually a little higher than the "5". On the
ebay example, the "9" is in line with the "5", and the undertype appears above the "9".
2. The star before 8R is "fat" and lumpy, but the star in Resplandores and Stacks is slimmer and "pointier".
3. The Lettering seems fatter, almost like its been soldered on. The "Z", the "8" and "R" in 8R, the "M" in the assayers' initials all look too "fat".
4. The dentils look too "receded" from the lettering -- in the Stacks and Resplandores examples the dentils are more intrusive. I understand that this could be a planchet issue, but in Zs examples I see, if one side has little to no dentil presence, the other side usually has "excessively large dentils".
5. On the reverse, the Eagle head looks a little off to me.
I understand why the overdating occurs, and I understand that Zacatecas had poor dies and quality issues, but this seems a little too neat. Also, would it be possible to have two different overdate dies? There's already a no-overdate variety for this date, and Resplandores only shows one overdate example. If I understand correctly, the difference in overdating (if this was genuine) would have to mean there would be 2 entirely different dies.
Perhaps this is a standard 1859? Or one that has been tampered with to take it from a common coin to a scarcer one? Let me know if I'm off-base, or if I am actually getting the hang of this.