I think the whole postmark area puzzles a good deal of stamp sellers and the majority postcard sellers (I include myself in that
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Cambrensis is right - the A & H reference followed by a number will correspond to a postmark detailed in the book/publication.
Ray can you scan an image or two of what you have? would be interested to have a look, not that I will be able to provide any help unless googling the info.
Last year I listed a whole batch of 70's and 80's postcards with specialist type postmarks on the back, I put the details of the postmarks in the title... 20 sold within the first 10 minutes.. followed by another 20 odd within a couple of days. In total I had around 120 and the whole lot has now been sold on eBid. Looking around it does seem to be an area where buyers have all the knowledge, if a seller can meet that knowledge and list accordingly then it could be extremely profitable.
I should really purchase the Gibbons 2013 postmark catalogue and teach myself something.