My late grandfather was a career soldier in the British Army. He joined up in 1936 initially serving in what became the RAC in North West India. I have a letter addressed to him as M/Sgt Jackson 25th Dragoons I'd always thought that he was more of a mechanic / transporter than a tank crew member (although he may have been tank driver). Does anyone know what M/Sgt means? The US Army appears to have a Master Seargeant rank but I don't think that's applicable for British Army. Furthermore I am assuming that its not the notation for Seargeant Major. Is there such a thing as Mechanic Seargeant ? Any help appreciated.