Call me by your number - 00 b Introduction

From the 'black penny in 1840, till the emission of 1883, plate numbers can be found on the stamps.
Each of the plates had 240 stamps. Most of them were issued on sheets of 20 rows and 12 columns.

An option would have been to 'number' those rows and columns, but letters were chosen instead.
Rows went from A to T, and columns from A to L; resulting in 240 stamps from AA to TL.

The letters to determinate, are the ones on the bottom of the stamp.
Below is a stamp (plate 22) - position K D (not DK !) - so row 11, stamp 4

plate 22 - position KD

One special version of the black penny, is with letters VR by the way.
These do not appear on a 'normal' sheet of 240 (nor does RV), they refer to the Latin Victoria Regina (Queen Victoria) and were used as service (official) stamps. 

Not only one can start looking for all possible plate numbers of one particular issue, (not always mentioned in regular catalogs by the way), but also the different positions of each stamp within the different plates.

For the depicted stamp above, there were 17 plates with a pink 2 1/2d stamp, and 7 plates (17 till 23) with the blue version. A total of 5760 'different' stamps to search for...

to be continued ...