'92 Mexico Encuentro De Dos Mundos - Souvenir Sheet - Postmarks?

Hello,

I found this Mexico Souvenir sheet in my Mexico stamps. are those two postmarks on this very large stamp? seems like this "stamp" would be too large to mail.

Thank you in advance.

Sc#1731 1992 "Human Culture" by Camarena CV: circa $21 / $5
107mm x 84mm
Opinion.
Not a large imperf sheet by any means compared to some other countries.
Can be used on Parcels and large format envelopes.

The trend over the years is to issue ever larger format stamps to trigger interest in country's stamps.
Postal services take second place to Revenue raising.

The Postmark/s look genuine albeit I do not recall seeing a rectangle Pmk before from Mexico.
Not a big fan of the Rectangle Pmks (Canada) they rarely present in full impression.

Thank you, was having a hard time finding it because I was searching in Spanish. Too bad it was not left on the parcel or envelope - that would have been cool to see. I also have not seen another postmark like that one.

I found a few buddies of "Human Culture" as well.

Mrita,
perhaps you care to offer a close up of the Postmark?
I can see "Negros" or something similar.

Yes! of course :) Piedras Negras Coahila. Here you go. I cannot make out what the word above it says. I also included a picture of the oval postmark (bluish), and the back.

Aha! Thank you, then it is a genuine Pmk, possibly a hand held Hammer,
maybe even rubber, to facilitate difficult surfaces to cancellation.