Hello, I think my recent thread could be interesting for you, see also chasa's answer from yesterday:
https://www.stampcommunity.org/topi...57714#503711I learned now that the BEP printing is the only one which was really highly standardized with quality control so there are nearly no inverts or errors. with all other precancel types, like your one, it's more common to have inverts or errors or 2 precancels printed too close like in your case. If it's a common precancel on this 15c stamp I don't know.