Image of a <a href="https://en.wikipedia.org/wiki/B61_nuclear_bomb" class="extiw" title="w:B61 nuclear bomb">B-61</a> <a href="https://en.wikipedia.org/wiki/thermonuclear_weapon" class="extiw" title="w:thermonuclear weapon">thermonuclear weapon</a>. In the back it is assembled, in the middle it is divided into its major subcomponents, in the front it is almost completely disassembled. The <a href="https://en.wikipedia.org/wiki/warhead" class="extiw" title="w:warhead">warhead</a> is contained in the bullet-shaped silver canister (see <a href="//commons.wikimedia.org/wiki/File:W80_nuclear_warhead.jpg" title="File:W80 nuclear warhead.jpg">Image:W80_nuclear_warhead.jpg</a> for a different, but similarly shaped, warhead casing).
US government DOD and/or DOE
Since 1945 (25 November 2007 (according to <a href="https://en.wikipedia.org/wiki/Exchangeable_image_file_format" class="extiw" title="en:Exchangeable image file format">Exif</a> data))
Immediate source: Chuck Hansen, <i>The Swords of Armageddon: U.S. Nuclear Weapons Development Since 1945</i> (Sunnyvale, CA: Chukelea Publications, 1995)<a rel="nofollow" class="external autonumber" href="http://www.uscoldwar.com/">[1]</a>