Going through my Concise to list out the 1st and 2nd class security stamps with year and source codes I find myself at odds with Gibbons over differentiating stamps because the backing paper they are supplied on is different. Yes I know that it sometimes means the printer changed.
OK I can see that the Backing paper can be one of three ways (at present) plain, with Royal Mail imprinted and with the same but with alternate pairs of lines inverted.
Now while on the original paper this is seen, once used it will not be, my query or problem is that the stamp itself is not different merely the backing paper.
Does this mean I can now collect used stamps on different coloured envelopes as being varieties? Yep guess if I want to I can, but I won't.
Ok rant over, back to being grumpy old man.