This a Soviet military badge for Kalmyks from the Russian Civil War. The hammer and plow at the top as well as the swastika in the center show that this particular insignia was used sometime between 1919-1922. The hammer and plow was replaced by the hammer and sickle in 1922 in the Red Army, but I do not know when Kalmyk and Buriat units were no longer allowed to use the swastika. I am guessing that it was outlawed sometime during the anti-religious campaigns of the early 1930s since the swastika is most definitely a Buddhist religious symbol. So here we have an early Soviet military badge combining the old hammer and plow with the Buddhist swastika along with a red star, wreath, and the letters RSFSR (Russian Soviet Federated Socialist Republics).