6.5x54 Mannlicher-Schoenauer, the 6.5 Creedmoor of its day. If the Internet had existed back then, World War One might have started even sooner, due to arguments over the 6.5x54 M-S and OBVIOUSLY much more suitable cartridges.
Big deal...I note that just after the 7x64 was created by the lord himself WW1 ground to a halt...obviously all were simply dazzled by the excellence.