Maximilian ruled Mexico from 1864 to 1867. This peso, along with a gold 20 pesos coin, was his primary numismatic (coin collector) contribution. There are three mint marks used, Mo, Pi and Go. Our picture has the common Mo (Mexico City) mint mark, which shows a small o hovering above a large M. If you have one with a Go mint mark, that's the big time. The Pi mint mark is like the Mo Mint mark.
Here are some approximate catalog values for these grand old Mexican beauties.
1866 to 1867, Mo and Pi mint mark:
worn: $50 US dollars catalog value
average circulated (like our picture): $75
well preserved: $250
fully uncirculated: $800
1866, Go mint mark:
worn: $500 US dollars catalog value
average circulated (like our picture): $750
well preserved: $1100
fully uncirculated: $3500
Because the value of this coin rises swiftly with condition, watch out for cleaned specimens. For examples of cleaning, and for the proper interpetation of the catalog values quoted above, refer to our Important Terminology page (link at upper left).