patch with black edge gold numbers and letters and light blue trouser stripe: air force. Red collar patch with black edge yellow letters and red trouser stripe: armoured troops. Black collar patch with red edge silver numbers and letters and red trouser stripe: engineers. Black collar patch with yellow edge silver numbers and letters and yellow trouser stripe: signals. From 1924 to 1934, the rank insignia have two colours. The colour of collar patch and the colour of collar patch's edge indicating the corps: Crimson with black edge: infantry and all troops services Blue with black edge: cavalry Black with bright red edge: artillery, armoured troops Light blue with black edge: air force Black with blue edge: technical corps (radio communications, engineers, chemicals, technical military schools, road construction, pipeline units, building and airbase construction, military topography service) Dark green with bright red edge: medical and veterinary services, administrative service, judge advocates From 1935 to 1942, the rank insignia have two colours. The colour of collar patch and colour of collar patch's edge indicating the corps: Crimson with black edge: infantry and all troops services Blue with black edge: cavalry Black with bright red edge: artillery Velvet black with bright red edge: armored troops Light blue with black edge: air force Black with blue edge: technical corps Black with black edge: chemicals corps Dark green with bright red edge: medical and veterinary services, administrative service From 1943 to 1955, the rank insignia have two colours. Colour of shoulder board and edge colour indicating the corps: Crimson with black edge: infantry, mechanized and motorized infantry Blue with black edge: cavalry Black with bright red edge: artillery, armored troops Light blue with black edge: air force, airborne troops, air technical services Black with black edge: technical corps Dark green with bright red edge: medical and veterinary services From December 1955 to 1970, the colours were changed to: Crimson: infantry, mechanized and motorized infantry, airborne troops Black: artillery, armoured troops, technical corps Light blue: air force Dark green: medical and veterinary services Red: high officers (all branches) From 1970 to 1991(93): Red: infantry, military educational institutions Light blue: Air Force, airborne troops, air technical services Black: artillery, armoured troops, technical corps and navy In March 1956, general officers' stars were changed to gold. Letter codes The letters over the shoulder marks, since 1972, stand for: ВВ (Внутренние войска, Vnutrennie voiska) – Interior Ministry's troops