


These would be considered in the "Errors & Freaks" category, I believe.
I have some that are inked inside and some that are albino also.
I also have some that are half-inked and some that are over-inked.
The United Postal Stationary Society US catalog might mention these. I will look for my catalog.
Envelopes with colorless indicia from sheet fed presses are called albinos, and typically are valued in the single digit range.
If it is from a web fed press, then it is called a missing color (or color omitted) error and typically are valued in the three digit range.
The reversed image on the inside is called "offset". You get those when an envelope blank fails to move through the press and the ink is instead smeared on the platen. The next guy though then gets the offset image on his backside.
Nice EFOs.

re: stamped envelopes
These would be considered in the "Errors & Freaks" category, I believe.
I have some that are inked inside and some that are albino also.
I also have some that are half-inked and some that are over-inked.

re: stamped envelopes
The United Postal Stationary Society US catalog might mention these. I will look for my catalog.
re: stamped envelopes
Envelopes with colorless indicia from sheet fed presses are called albinos, and typically are valued in the single digit range.
If it is from a web fed press, then it is called a missing color (or color omitted) error and typically are valued in the three digit range.
The reversed image on the inside is called "offset". You get those when an envelope blank fails to move through the press and the ink is instead smeared on the platen. The next guy though then gets the offset image on his backside.
Nice EFOs.