The SIG company of Neuhausen Switzerland spent the 1920s, 30s, and 40s working on developmental semiauto rifles to sell both to the Swiss military and abroad. One of the experimental models in the succession of designs was the Model U, of which 16 were made in caliber 7.5x55mm Swiss. It was a gas-tappet operated action with a tilting bolt, and included a permanently mounted 1.8x optical sight on the left side of the receiver (the same type as used in the K31/42 marksman’s rifle). The Model U was made in 1942 and 1943, to typical Swiss levels of quality and precision. Like the designs both before and after, it was a valuable iterative step for SIG but not a rifle which would find any military or commercial sales.