A trophy Sterling-Patchett, with an interesting back story
The Sterling-Patchett Mk 5 was a silenced version of the Sterling Submachine-gun. The modification was the work of George Patchett, who had originally designed the Sterling itself. The Mk 5 was adopted by the British armed forces as the Gun, Sub-machine, 9mm L34A1.
This is the commercially sold version with a “crinkle” finish, which featured a wooden foregrip to protect the firer’s hand from the integral suppressor unit, which became hot from the propellant gas which vented into it upon firing:

Copyright: © IWM. Original Source: http://www.iwm.org.uk/collections/item/object/30029460
This particular gun was captured from Argentinian forces during the 1982 Falklands Conflict by the British Army in June 1982 along with 20,000~ other sundry surrendered arms. It was issued (along with standard versions of the Sterling SMG) to the Argentine Marines, and was most notably used by their assault commandos – the Buzos Tacticos – during the initial stages of the Argentine invasion.