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Source : http://www.olive-drab.com/od_other_firearms_smg_sten.php3

"Olive-Drab Military Photo Credits Olive-Drab is famous for its extensive military photo collection with examples of mostly American Army, Navy, Air Force, USMC photos and graphics on every page. Plus there is a constantly changing selection of random photos shown on the home page and also the gallery of historic military photos and posters.

Unless otherwise noted, these photos and posters are drawn from the immense collections of the U.S. Government in the National Archives, the archives of the military services, and compilations of these photos maintained by universities and foundations. Such photos and posters are in the public domain and may be used for any lawful purpose" This is a Sten Mk IIS, misidentified in the title as a "Mk IVS."