DENOMINATIONS
Apparently the forgers were clever enough to develop product that would be in demand. They seemed to focus their efforts on the 25 centavos forgeries, but produced some pretty good quantities of 50 centavos stamps as well. 6, 12 and 100 centavos stamps can be difficult to find, especially the 6 centavos.
The 12 centavos stamps can also be difficult to find. And they are also difficult to identify. The 2nd period stamps, with the inverted district # and date, are easier because of the inversion. But the 12s can be difficult to spot otherwise.
1868 Issue of Mexico, The Great Postal
Fraud
Types of Mexico (TIPOs)