Inverted Machine Cancellation

I'm finally getting around to scanning some of the many covers and postcards I fished out of the bargain bins at the Portland APS show. Here is one of the most curious -- a 1921 #10 cover from Yakima, Wash. with an inverted date slug! I didn't think this was even possible in a machine cancellation. Wasn't there some safeguard preventing the slug from being inserted upside down?

Does anyone know the relative scarcity of an error like this? It's the first time I've seen anything like it.

It was possible in some machines, particularly Universals like this one. For the most part they are considered novelties and would sell for a few dollars.

The term "error" tends to have a specific meaning in philately that refers to a major mistake in the production or printing of a stamp or postal stationery - an example is the inverted jenny US airmail stamp. There are two related terms - freaks and oddities - that refer to lesser mistakes in the production or printing of a stamp or postal stationery. For something like this that any postal employee could do on purpose or by mistake any time, any day, I agree with paperhistory that this might more accurately be termed something like a "novelty" or perhaps a "curiosity". I also would agree that on its best day it might bring a couple of dollars at the most. I think it would be a fun and very inexpensive hobby to collect this kind of oddity - either where the whole date slug is inverted or just the date numbers are inverted. It would be a unique collection and fun to put together.

Terminology:
Slug: the small removable pieces in the center containing the month, day, time, or year data.
Dial: the entire circular (or other shape) town portion, which contains the slugs.
Inverts of both are the result of employee error.

The original illustration has the slugs inserted correctly into the dial. It is the dial which is inverted in the machine.

Moving onward, I agree with paperhistory, inverted dials are novelties typically commanding only a small premium over the normal configurations. Here are additional examples from Universal machines:



While many machine makers must have notched the canceling machine dials to prevent inverted insertions, it appears some models of the Universal machines were purposely made to be adaptable. Consider the return to sender markings, where the dial is inverted to read normally.



Here are some accidentally inverted dials from Columbia machines.



Here are normal and inverted dials from a Columbia machine as received use. Is it really an error or intentional?



The dial portion of the Barry machines was a combination of rectangular slugs of various sizes, here with the town portion inverted within the dial.



It is also possible with some machines to invert the killer, but that is often not obvious. And in even fewer cases, parts from one manufacturer fit another manufacturer's machine.

John, thank you for posting all those examples and for the terminology explanation. I knew "slug" wasn't really correct and now I understand the term "dial." I'm getting a great education!

An eye-catching inverted date slug: the only example I have ever seen with the arced year-date inverted on a facer-canceller type of machine. (cropped from a full envelope)

I have a cover on which only the year is inverted: 1661.

Bumping this older thread. I have a large amount of cancels that I am slowly going through, looking for birthdates, etc. This one is relatively modern (1989) and the year is definitely inverted. I guess it still happens.

I posted this card on another thread, then realized the year slug was inverted, so I'll add it here, too.