Switzerland entered the 20th century with a service rifle designed around 1889, the Schmidt-Rubin. This was a straight-pull bolt action repeater, and it fired a 7.5x53.5mm cartridge known as the GP90 (1890). Around 1905, Germany came up with a new military cartridge, with a pointed (spitzer) bullet and smokeless powder. Switzerland responded with the GP11 round (for Gewehrpatrone 1911) - a 7.5x55mm cartridge, with a 174 grain spitzer bullet of 0.3087" diameter on it that developed approximately 2640 fps. This round was used in rebarreled 1889 Schmidt-Rubins, in the 1913-introduced 1911 Rifle, and in the 1931 shorter K31. It continued in service until 1983, used in the StGw 57 (Sturmgewehr 1957).
The round develops energy between the American .308 Winchester and .30-06 Springfield cartridges, with a lower operating pressure. In its GP11 form, this round is extremely accurate, to the point that enthusiasts with K31 rifles and surplus GP90 cartridges are able to compete effectively with dedicated precision ammunition and target rifles, which speaks extremely highly of Swiss arms design and manufacturing. It can be had, as of 2015, intermittently in the US as GP11 surplus, although those cartridges are Berdan primed; and it is occasionally manufactured by companies such as Prvi Partizan and Wolf in modern Boxer-primed brass. It can be reloaded using standard 30-caliber (.308) projectiles.
It is likely referred to as 'Swiss' to prevent confusion with 7.5x54mm MAS, also known as 7.5 French.