New Mexico Portrait 8 Reales discovery - 1797/6 overdate

Ever since I started collecting Mexico City Portrait 8 Reales varieties about a decade ago, I’ve held a consistent belief: with every major design change - be it a new date, assayer, or monarch - there’s a high likelihood that existing dies were reworked by the mint’s die sinkers to reflect the update.
Mexico City produced millions of 8 Reales during this period, and knowing the approximate die lifespan of 20,000-30,000 strikes, it’s safe to estimate that anywhere from 50 dies in the earlier years to over 250 dies in the peak production years were used annually. Considering how labor-intensive die sinking was - and the fact that die steel was a scarce and valuable commodity - it makes sense that working dies would be repunched or modified rather than discarded when minor changes occurred.
This idea has shaped how I collect. I’ve always kept an open mind that not all varieties are yet known - some just haven’t surfaced. And by following that principle, I’ve been fortunate to uncover a number of new varieties over the years.
Here’s another one I’m excited to share.
For 1797, there has long been speculation around a possible 1797/6 overdate. Brad Yonaka and I have both noted examples showing minor chipping in the digits that could - if you squint a bit - pass as evidence of an overdate. Brad, in his reference, rightly notes: “A reported 1797/6 overdate (not listed) was observed but is unclear and the variety requires additional evidence.” I also documented a few candidates, but like the example Brad saw, it was ultimately inconclusive.
Now, with this new piece, I believe we finally have confirmation. The underlying digit shows the kind of distinct arch you’d expect from a true overdate. I shared it with Brad, and he agrees - this coin confirms the variety.
I'll need to do some conservation to remote all the green and then at some point get it slabbed by PCGS with proper attribution. But for now - the hunt continues!
Comments
Now the full write up! Cool @TwoKopeiki
Huge news! Congratulations on the discovery.
Congrats TwoKopeiki on a great discovery! Nice writeup!
Thanks everyone. I know the coin is not what you would call an attractive specimen, but it's the first one of its kind
8 Reales Madness Collection
Is that maybe a zero? - To me the zero it is like an ellipse shape same as on your coin the six on the bottom is wider.

Charles III Album
Charles III Portrait Set
Charles IV Album
Charles IV Portrait Set
Spanish Colonial Pillar Set
Awesome overlay. Thanks for putting in the time!
8 Reales Madness Collection
Congrats on this find! It might be more effort than it's worth since what you have seems conclusive, but maybe you could look through 1796 coins and match the exact die using the spacing or positioning of the legends or some other pick up points, since now there is reason to believe you will find a perfect match.
Congrats always cool to find new varieties!!!
Can you post after acetone images?
You are one of the collectors defining your field. Well done!
Latin American Collection
Thank you fellas. Always appreciate the engagement from this community.
@Euclid It might be a while until I have time to do a more comprehensive die study that would go as far as identifying the old 1796 die.
@The_American_Frontier I will post images after the acetone treatment.
8 Reales Madness Collection
As promised - results after treatment.
Original -> Acetone overnight soak -> 10 minute soak in White Vinegar
8 Reales Madness Collection
Much better now. Do you think another few acetone treatments would take the green out of those pitted holes? I would give it a try. I would do 24 hours each side a few more times. Can't hurt and may even help.
Sometimes a coin needs more than a few treatments. You can also roll a q-tip dipped in acetone in those areas after each new bath. Do not rub just roll the cotton on those spots that seem to still have some green.
I would keep doing this till all of it is gone. Otherwise the PVC may just spread again over time. Your not going to hurt the coin it would not grade numerical with the pitted holes anyways so mine as well finish the job and get all the green spots 100% off.
If you chose to skip this I would suggest you do no place it with your other coins and keep a close eye on it because as mentioned there is a good chance the PVC will spread on the coin again or to other coins if in contact with them.
Acetone did very little to remove the verdigris. 3rd image is after the vinegar treatment.
8 Reales Madness Collection
Have you considered olive oil? I am not confident that it will help in view of what you have already tried. Congrats on the overdate confirmation. There is something gratifying about finding a discovery coin.
Edited to add… would the excess metal below the portrait and next to the 7 that looks like a blob where the dot should be play into a possible subset of the initial overdate variety? Or is this some type of cud? It does not strike me as being a cud but I suspect others may chime in on this.
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Hopefully the remnants of the underdate hasn’t been soaked off
Latin American Collection
You probably know this but you can use Verdi Care. Some say lemon juice works as well on verdigris (you may have to rub the coin). Anyways good luck!!!
I've considered it as soon as it became apparent that some kind of an acidic solution would be required.
8 Reales Madness Collection
The other spots are die deterioration / chipping. It would be interesting to find the other die state examples. Potentially ties to @Euclid question about matching it back to the original 1796 die and seeing if the deterioration is present there. That would be a cool find - a 1796 example with the early stage die showing these markers!
8 Reales Madness Collection
Will this one be the same overdate? or something else?


@ELuis to me that falls in the category of "maybe, but not enough evidence remaining". Similar to the top 2 examples I posted earlier in the thread. I don't have that specific die cataloged - can you share the reverse photo?
8 Reales Madness Collection
Congrats Roman, that's really cool.
Here it is:
