The powder used in wartime DI production (the original Type Z powder) was a tubular, progressive single-based powder very close to IMR-4895. It was based on the Nobel Neonite patents.
Mark VIIG designation was used twice, believe it or not. Originally, this was a WW ONE designation for the first tracer, but this was changed in the 1920s to Cartridge, Small Arms, Calibre .303, G Mark II. The G arose later on, toward the end of the SECOND war, to denote the new bullet crimp: at the case mouth rather than the triple stab-crimp halfway down the neck. The new bullet also had the crimping groove moved to accommodate this design change. It was functionally identical to the regular Mark VII Ball round but (possibly) not quite as tolerant of being bashed about in Vickers Gun feed-blocks.
DI primers were ALL noncorrosive and nonmercuric and the brass was the best military brass I have ever encountered.
1944, by the way, is the year the casings were manufactured.