It was known as 11.15x60Rmm Mauser and 11x60Rmm Mauser. It is a rimmed cartridge designed by Paul Mauser and adopted by the German military in 1871 with the M71 bolt action, single shot Mauser rifle. The cartridge became a popular sporting cartridge in Europe and East Africa.

http://www.buffaloarms.com/browse.cfm/4,4190.html

The original loading was:
370grn paper patched
77gr black powder
mv 1430
ft/lbs 1680

Pete