British Military binocular 7 x 50 bino prism No 5 Mk IV Ross London
Apart from general sales of binoculars, Ross supplied the military during WW 1 and WW 2. The most well known of the military binoculars are the British Army's 7 x 50 Prismatic No5. These were derived from the Ross Stepnite, which was introduced in 1930. The military Mk IV version of 1944 could also be filled with dry air to stop condensation and fungus growth.
O.S.735 G.A. would stand for Optical Store : Drawing number 735 showing the general arrangement of the design.