I have a bunch of Mexico Revenue stamps and this particular stamp intrigued me. So here's a little information.
Mercancías Cotizadas - Priced Merchandise: Short lived series of revenue stamps issues from1881-1884 to apply a tax on priced merchandise. These were rouletted or perf 12, and on wove paper.
Roberts Catalog of Mexico Revenue Stamps - page 185
1881 Ocampo - Roberts MC 5 - 10 Cents - Vermillion
CUERNAVACA Overprint 14 3/4 x 2 3/4 MM
RetroReveal to see what the Overprint could be
Overprint looks to be CUERNAVACA. I tried to verify this with the Roberts catalog.