Guatemala The "Impossible" Cover

This interesting cover is pictured on p.46 in the GUATEMALA I, the Bible of Guatemala collectors and is described as the "impossible cover". I don't understand why the author used the word "impossible", because human error is always very possible, even twice on the same cover. The year date 74 is inverted in the red postmark and the date 31 is inverted in the black postmark that canceled the stamp. 8 covers are known with this value and this is the only cover with the error postmarks.

Speaking from complete ignorance, my first thoughts are:

- inverted date elements are certainly possible, and

- two different cancelers having different inverted date elements is possible.

But this clerk used each of these once, rather than using one of these twice.

That seems unlikely, eh?

Cheers,

/s/ ikeyPikey

The red paquettes strike off the stamp is not uncommon for Guatemala covers. So, this is certainly in the realm of possibility, but a postal clerk having some "fun" seems just as likely as two completely coincidental legitimate inverted slugs.

"Impossible" cover has a better ring to it than "really quite unlikely when you think about it" cover, so I can understand the hyperbole.

Then again, there are a lot of fabricated covers in the world that are well and truly impossible, so I might have selected a different word.