I found a drawing of the rifle in "Big Game Rifles and Cartridges" by Keith on page 57. In this illustration it has no blocks for a target scope, but instead a quarter rib and a multiple leaf rear sight with a banded ramp front sight. No recoil pad. There is a discussion of the .280 DuBiel cartridge from page 54 to page 58, but no mention of a .280 OKH.