U420 Precancel Entire-Dayton Ohio

This interesting precanceled 2c postal stationery item has many of us scratching our heads in puzzlement. There was no 2c precanceled rate at the time this was issued. The envelope contractor was located in Dayton, Ohio. Suggestions as to how this envelope came to be include 1)accidentally tucked into a box of the proper 1c envelopes, 2) an essay or proof. Examination seems to indicate that it is a genuine precancel applied by the envelope contractor. There are 3 known.

Can anyone add anything? Proof would be nice, not just speculation.

Need better scan. Just give us a hi-res on the indicium, and also tell us size, knife, watermark, etc.

2220-26
Precancel envelope catalog 1b1 ? 41 26

One possibility: a press was switched from doing normal 1 cent precancelled envelopes to the 2 cent die. The precanceling die was mistakenly left in (for a brief period).

The Scott No. for that stamped envelope would seem to be U429 (not U420).

Yes, wt, pardon my typo.