This is a very interesting cover. It bears a stamp that was originally overprinted "Mexico" for usage in Mexico City, but it was then taken in by the Puebla post master and overprinted with the "PUEBLA" district name (barely visible at the 3 o'clock position on the stamp, toward the top of the letter) and used by the stagecoach company for the cover to be sent to Mexico City. The double overprint of Mexico/Puebla makes the stamp a "habilitado", see the dialog in Veracruz.