Today in Postal History

This interesting uprated postal card was mailed from Mexico City
where it received two strikes from a MEXICO . D F duplex with a DF killer.
Interestingly, the message is dated May 15.
Someone was having calendar troubles.

There is also an oversized transit CDS in Spanish for May 17.
It is from a port city, probably Tampico, in Tamaulipas (state) on the Caribbean coast northeast of Mexico City.*

The postal card's arrival in Uruguay was noted by the DOMICILIO letter carrier mark dated July 5.**

The postal card was marked Servicio Urbano (city service?) and
bore an indicia similar to the 1 centavo green letter carrier of 1895 and 1898.
It was uprated by the addition of a 2 centavo scarlet letter carrier probably from the 1898 series (Scott 280).
Watermarking, or possibly color shades,  would be required to
differentiate the stamp from similar stamps issued in 1895, 1896, and 1897 (Scott 243, 258, or 270).
It is clearly not one of the odd perforation varieties scattered in these series.

Note the message side includes a handstamp with the sender's return address.
The handstamp was evidently modified by removal of the address which has been added in script.

As one might expect, the card deals with a philatelic transaction.
The sender has transmitted some old stamps and tells the recipient that they can be returned if not to his liking.*

*Thanks to rpm992 for this added information.
**Thanks to Bill Longley for identification of the DOMICILIO mark as a letter carrier mark.