GB 1d Black & Red Matched Pairs
The GB Line Engraved is 'unique' in that of the Black Plate printings, some plates were used to print in Red ink. These are known as Red from Black Plates.
As a consequence of this it is possible to find both printings of the same plate in both colours. These are Matched Pairs. However due to early repairs to the plates they are either identical or can have slight distinguishing marks.
In addition Plate 1a was repaired to make Plate 1b which was printed in both Black and Red, so it is possible to find Plate 1a in Black, 1b in Black and 1b in Red as a matched Trio.
Here are some examples.
Plate 1a & 1b-1e
N.B. Further repairs to what became Plate 1b were necessitated resulting in reds from Plate 1c-1e, not all units were further repaired.
This allows various combinations of matched pairs to exist for plate 1.