General outline history
The plate was completed 19th February 1864 (engraving book), was hardened 24th February 1864 (hardening book), registered and put to press 1st March 1864 (W&C). Earliest known use 14th May 1864 (Allan Olliver). It appears again in the engraving book showing that 87 labels were repaired on 4th February 1868. Defaced 23rd March 1868 with 510,300 sheets printed (W&C).
Many of the positions have a description supplied by the Penny Plates Study Circle (PPSC) as reported by GC Akerman in the GBJ Vol 12, p83-4 and reproduced in the detailed study below.
Comments
Judging by comments seen it would appear that this plate saw repairs on two separate occasions. Winston Hollins has a cover 85 AF in state 2 dated 11 May 1866 so the first repair was some time before this. The second repair was completed at the recorded date of 4th February 1868, just before defacement.
I have come across several impressions that exhibit what looks like a slight transfer roller line in the upper-center of the east margin (EE, EG, KD, MD, QC, QE and TB so far). I am not convinced that this is evidence of a second state in these impressions and my gut feeling is that there was a slight distortion to the transfer roller at this point. If this is correct, the blur would be an indication of an early print soon after initial entry or subsequent re-entry. More examples will help with the analysis.
It would appear that stamps from this plate are slightly out of square, leaning slightly to the left. I need to examine and compare more stamps to see if it is a plate feature. [Later.] It would seem that this is a common feature of this plate. The likely cause would have been a slightly warped transfer roller. It would be interesting to review the other plates found on the same transfer roller to see if they are affected also.
Detailed study
Varieties of printing and usage (As per the PPSC)
AP
Feb 2016 - Jan 2017