It looks like a reentry position from plate 1.
Here it is (I think) at 7L1.

EDIT: Apparently all of plate 1 was recut.
"the fact exists that every position on Plate 1 was recut.
While it is not probable, still it is possible that the recutting was done after the plate was in use for a short period, but as no stamps are known which do not show recutting, we assume the recutting was done before the plate was turned over to the printers."