The EM-2 is one of the big what-ifs of military adoption history.
The EM-2 is a rare thing for small arms circa 1950 as a intermediate caliber bullpup. The round conceived for the futuristic looking rife being the .280 British round. Variants also being in 6.25×43mm, 7×49mm and 7.62mm. The British adopted it for about 30 seconds then changed their mind. Going on to use the now famous FN FAL in 7.62MM NATO.
This gun belonged to the designer , Stefan Janson. Following the EM-2 project , Janson came to the US and worked for Winchester on the SALVO project, at some point he gave the EM-2 to the company who later gave it to the Cody Firearms Museum.
The British apparently really liked the idea of the bullpup rifle. The L85/SA80 becoming their standard service rifle since 1985. Though its record has been…questionable.