This one is beauty. The only way I can explain this stamp is to offer the following scenario:
Take a retired plate and give it to your apprentice to practice on using the transfer roll, burnishing out mistakes and the retouching. OOPS the plate went into production, probably to make up a production shortage.
This is what I have observed so far:
In the lower left numeral box base I count three base horizontal lines (lowest the complete width of stamp) and four vertical lines (right most well removed, 0.15mm, from the frameline).
At the top of the stamp there is a oval remnant/retouch line above the frameline.
And then there's the upper right corner, re-entry and touchup? Your guess as good as mine.
Look at the background lines entering into the letters; particularly the D and A.
And, of course, the 1s and, now the retouches:
Most noteworthy, new lines (not in original design) have been added in the space between the outer frameline and the stamp body above the crown. Can't be slips. They seem a deliberate attempt to give more definition to the top of the crown.
There is also an extra line (slip?) above the bridge of the nose that runs into the eye.
The area of retouched background lines is vast and inconsistent in strength.
Edgelines are also inconsistent and some down right sloppy.
Also the right numeral box outside frameline, I can't discern a continuous true vertical line.
Finally, in support of my apprentice theory, considering the extent of retouching, there are weak areas and lines un-retouched (particularly the upper left spandrel). This plate image is so sub-quality I can't envision it being used except by accident or through desperation; hence a practice plate put back into production.