It is possible that the RHA type belt with metal buckle is that of 3rd Regiment RHA (although the dimensions should be Royal Blue 15/16, Yellow 3/8, Royal Blue 15/16 inch). The design and colour of the current RHA belt (Royal Blue 1 1/8?, Yellow ¼, Royal Blue 1 1/8 inch), was not introduced until 1970, when it was decided that ALL the RHA would wear the same belt. This did not stop the Bty belts being worn, but it did bring in a belt for all those members of the RHA who did not have a belt of their own.
If the suggestion is correct about the Radfan then the only 'Sphinx' RHA Battery is F (Sphinx) Parachute Battery RHA (part of 7th Parachute Regiment RHA since 1961) who have had their own belt since 1965, colours as per RHA belt with a maroon edge top and bottom.