GB Machins: Do Phosphor Cylinders 13A And 14A Exist?

Hello, wise and helpful experts!

I've been compiling a table of phosphor cylinders used for GB Machin definitives printed by Harrison and Sons from 1971 onwards. My only source for this compilation is Stanley Gibbons - sadly, Deegam has no information, nor do the online chapters of the Connoisseur Catalogue.

As you can see in my table (attached below), cylinders 13A and 14A are included by Gibbons in their useful introductory list of all phosphor cylinders, but their detailed lists of individual stamps contain only one use each of cylinders 13 and 14 (probably in 1973 only), and no use at all of cylinders 13A and 14A.

It occurred to me that cylinder numbers 13A and 14A might have been used on the dot panes while 13 and 14 were used on the no-dot panes, but the cylinder blocks from my collection refute this hypothesis.

It also occurred to me that these cylinders might have been used only for regional issues, like cylinders 10, 11, 12, P19 etc (which are not included in my table yet), but both the regional cylinder blocks I own and the Gibbons listings refute this hypothesis too.

So do phosphor cylinders 13A and 14A exist or not? Or am I stupidly missing something obvious?


In the "cylinder numbers" column, S stands for small, L for large, and R for re-engraved. In the phosphor column, 2B, CB and AOP stand for two bars, centre bar and all-over phosphor; B3 and A represent different phosphor inks; and 150 or 250 are the photogravure screens measured in lines per inch. These details are irrelevant to my question, but may be of interest.
N.B. My table is a draft, not a finished publication, and hasn't been checked carefully for mistakes.