Help With Ethiopian Postage Due Stamps.

I've found these three Ethiopian stamps of King Menelik II, which I've seen online as Postage Due, but I can't find them in the Scoot and Yvert catalogs I have. What number is associated with their classification? I've found some information here https://touchstamps.com/Issue/Detai...e-due-stamps , but the Yvert number is accompanied by "Mistake"...

12A,13A,14A in Stanley Gibbons catalogue.
https://www.doigsden.com/1896PostageDue.html

Thanks for the info!!!

Are the SG numbers 12A etc, or D12A etc?

It seems to me from the touchstamps.com description that Yvert lists the stamps as errors, not that the Yvert number is an error. But they're not errors, merely unissued stamps.

Since they lack the overprint to convert postage stamps into postage due stamps, perhaps they ought to be called unissued postage stamps, not unissued postage due stamps.

I'm surprised that SG gives them a catalogue number instead of a footnote. They seem to have had no purpose other than to provide collectors with something to stick in their albums. Nevertheless, they're very attractive labels!

They are truly beautiful stamps. I also have the coin from which the design is based, which is equally beautiful, and the fascinating Amharic typography stands out. Menelik was also a very curious figure, with details like the three electric chairs he bought for the country. However, when he realized that Ethiopia didn't have enough electrical capacity to operate them, he used them as thrones for receptions...