There are several things to keep in mind when attempting to qualify a district name overprint. The first thing is that many offices used multiple devices between 1856 and 1883. And in many cases these were created with different fonts so that, except for the name itself, there is little similarity between. Also, there were a few districts, usually those with minimal requirements for mail, that used the same overprinting device from start to finish. An example of one of these districts is Lerma. Lerma used only the single overprint throughout.

Another thing to keep in mind is that the district names were applied with liquid ink, and liquid ink spreads and seeps. And depending on the make-up of the ink, if very oily for instance, it could continue to spread for years after application. And the postmasters would use different ink from time-to-time. So one might observe two overprints applied with the same device but with different inks, where on one the ink seeped and broadened; and on the other the ink pretty much stayed put. When comparing these two overprints it might lead the observer to think that these are two different district name overprints.

Apparently all of the district name overprints were "hand held" devices and applied much like a cancel would have been applied. Some times one will encounter a cover where the district name was affixed partially on the stamp and partially on the cover, tying the stamp and cover. These cases are not rare, but are scarce. Some postmasters more than others did this. Campeche, for instance, had a postmaster that was notorious for this practice. Also, many of the district name overprints were wider than a stamp, and in thiese cases it is not uncommon to see the district name on the cover and on the stamp.

It is likely that various postmasters implemented the overprinting of the stamps differently. One postmaster, such as the Campeche postmaster mentioned above, would apply the district name right as the stamps were being affixed to the letter. Others applied the district name overprint to stamp stock long before usage, and for that matter long before they were cut individually for use. Often, the same ink was applied for the district name overprint and the cancel. Offices like Pachuca have some stunning examples with both a red district name and red cancel.