1854 cover to London with "short" 1d red

1854 Mourning cover to London franked with 1854 1d red on blued, wmk. SC perf. 16, a superb "short" square stamp (AB) from the top row of the sheet, cancelled with fair "156" Cork diamond, at left with a fine and almost complete, small straight-line MONKSTOWN CORK in light blue.
Despite small faults, most unusual and interesting.