Which riffle on which SIG SG 550 is based is a 5.56×45mm NATO assault rifle developed in the early 1970s by Schweizerische Industrie Gesellschaft?
SIG SG 550 The SG 550 is an assault rifle manufactured by Swiss Arms AG (formerly a division of Schweizerische Industrie Gesellschaft now known as Sig Holding AG) of Neuhausen, Switzerland. "SG" is an abbreviation for "Sturmgewehr", or "assault rifle". The rifle is based on the earlier 5.56mm SG 540 and is also known as the Fass 90 ("Fusil d'assaut" 90/"Fucile d'assalto" 90) in French/Italian or Stgw 90 in German ("Sturmgewehr" 90). 
MAS-49 rifle The MAS-49 is a French semi-automatic rifle that replaced various bolt action rifles as the French service rifle that was produced from 1949. It was designed and manufactured by the government-owned MAS arms factory. The French Army formal designation of the MAS-49 is Fusil Semi-automatique de 7,5mm Modele 1949 ("semi-automatic rifle of 7.5mm model 1949"). The MAS-49 semi-automatic rifle was produced in limited quantities (20,600 units), whereas the shorter and lighter variant, the MAS-49/56, was mass manufactured (275,240 units) and issued to all branches of the French military. Overall, the MAS-49 and 49/56 rifles gained the reputation of being accurate, reliable and easy to maintain in adverse environments. All the MAS-49 and 49/56 rifles feature a rail on the left side of their receivers to accommodate a designated rifle scope. The MAS-49 and MAS-49/56 were replaced as French service rifles by the FAMAS assault rifle in 1979.