Mexico 1837 8 Reales Planchet Adjustments Or PMD?

This 1837 Mexican 8 Reales has a flat central obv with an indentation and very flat rev center but lots of detail showing in other places on the coin.

The coin weighs 25.7 grams and the "general spec" is supposed to be closer to 27 grams.

My question is was this coin made this way, was the planchet worked before or maybe even after the strike so it was closer to the weight they wanted, or did someone remove silver from it a long time ago causeing actual PMD?

As I am learning about early Mexican coins I understand that they were very inconsisitant which led to many many interesting varieies.

Would like your feedback.

Thanks!