The Sten Mk5 (sometimes written Sten MkV) was really the Cadillac of the Sten series. It was designed in 1943, and featured a full wooden buttstock patterned after the No4 Enfield rifle, as well as a front sight abductor bayonet lugs for the Enfield. It has a wooden pistol grip as well (and early production examples also had a wooden vertical front grip). It was mechanically the same as the earlier Stens, simply with the fire control group moved forward to fit the pistol grip.

The Mk5 was not quite as insanely cheap and fast to make as the MkII and MkIII, but by the time it went into production British arms supply had largely caught up to demand, and they could afford to be a bit less economical. The Mk5 was really much better handling than earlier models, and was well liked, seeing combat as early as the invasion of Normandy in June 1944. In total, 527,428 of them were produced and they remained in service until the adoption of the L2 Sterling submachine gun in 1957 (and they were not completely phased out until at least the late 1960s).

Many thanks to the Royal Armouries for allowing me to film and disassemble this submachine guns! The NFC collection there - perhaps the best military small arms collection in Western Europe - is available by appointment to researchers:
https://royalarmouries.org/research/national-firearms-centre/

You can browse the various Armouries collections online here:
https://royalarmouries.org/collection/