Thank you gentlemen !
That was exciting whilst it lasted.
Per the Barefoot Catalogue "Telegraph Stamps of the World" (2013), which updates the long out-of-date Hiscock's "Telegraph & Telephone Stamps of the World" (1982), this is Barefoot #13a 30c lilac overprinted horizontally in blue, bisected on piece. Catalog value 20 UKP as such.
Shall save on my Album Page.
Not sure when Byrum created his catalogue, assume around 1950'sBAREFOOT
"This new catalogue lists telegraph and telephone stamps of the whole world, by country. It is the successor to the old Hiscocks catalogue of 1982. It lists all regular stamps, both those issued by national post offices and those produced by private companies (but does not include prepaid stationery for telegrams, nor telegram seals). It does include telephone stamps, e.g. those of Canada, Great Britain, India-Patiala, Belgium, France etc. In the catalogue, virtually all items are illustrated in full colour, some sections much expanded since Hiscocks, with up-to-date pricing for mint and for used."--Publisher description.