Manitowoc, WI Type 229 Precancel - Printing Error?

Is this precancel pair from Manitowoc, Wisconsin a known error or just a freak caused by poor inking? I think it's a Type 229:

Wt1, Reading your posting 9-8-11 of a pair of Manitowoc precancels, I didn't see any response so here goes. They are type 229's. I think the term error refers to mistakes made in the set up of the device, ie. numerals used for letters, inversion of letters, ommission of letters and mispellings. The problem with the "M", though slightly different, appears on attached stamps indicating to me either damage to the device or some kind of debris. If debris caused the "misprint" I would expect there to be a few more similar ones. If device damage caused it , there should be many more out there. It would be interesting to see a strip showing a pair like these with more stamps attached at top and bottom. This is just my evaluation of what I see.

Thanks. I suspect the cause of the "freak" is due to a damaged precancel device. I know it's nothing particularly valuable, but it does make for an interesting conversation piece.