In 1907 Vladimir Adrianov, a Russian engineer and military cartographer designed this military compass on a strap with lever to fit the needle in position. It simplicity of design, reliability, accuracy and the fact that it could be easily produced in large quantities made it popular. Through the years there were several changes in materials used (use of radioactive luminescent material stopped in the 1960’s). This one is all plastic with metal lever and real glass window as well as a genuine leather strap. It was produced in the 1970’s but looks never used in the field. A great piece of Russian military history and fun to use. It measures ca. 5 cm or 2 inches in diameter. See attached a short YouTube video on how it works. This is an earlier version (which sometimes alway were a bit radio active indicated by the reddish color of the luminous parts).