Egypt 20-Pa Blue From 1879 With Inverted Wmk, Are They Harder To Find?

Ok, so I am getting ready to start working on Egypt and have been busy gong through some of my Sphinx and Pyramid issues and noticed in my SG catalog that this stamp is valued higher, like 10x higher, with an inverted wmk.

Scott doesn't say anything about inverted wmks at all, so all I have is the SG catalog for reference.

I have 35 used copies of this stamp and the majority of them have the wmk inverted. Is the SG catalog a misprint? It just seems weird that I would have so many of them compared to the normal wmk?

Opinions?

It's like this?

Perf 12, yes, the majority are like that. About 15 of the 35 have the crescent under the star. One, I'm assuming, is considered inverted?