regret I don't see your can/mug in the Sowerby catalogue.
Am attaching a pic of 'Jacobean' tankards/mugs, again showing this 'cut-out' feature on the handles - I say 'Jacobean' because that is what two of them have in relief letters around the rim of the base - although all three have the mirror shiny outer part of the base, which I had understood to mean they were not U.K. made pieces.
However, on the basis that 'Jacobean' was Davidson's Tyneside re-branded name of the Rudolfova hut 'Lord' range - then, logically, these pieces were made in the U.K., and not Czechoslovakia, and are simply one more example of this odd handle feature which seems to have been peculiar to Davidson - or was it really a Rudolfova hut design feature that Davidson continued
The reason for waffling a little is that I'd assumed I would be able to find an illustration of a Czechoslvakian made example of this (Jacobean)tankard/mug (showing the handle cut-out), but I can't - despite looking in Pamela's French Markbheim catalogue and the Sklo Union book and CD.
None of which is particularly relevant to your mug - but grew out of my efforts looking at Davidson's handles with cut outs
As far as I can see Bagley didn't offer any commemorative mugs - and don't believe that Nazeing did either - so getting to the end of the road, regrettably.
My apologies for hijacking and going off the rails a bit, but hope it wasn't all boring, presumably no one else had any ideas?