An interesting thing about these transistors is they look like standard power transistors in a metal TO-3 package. However, the transistor itself is in a round

An interesting thing about these transistors is they look like standard power transistors in a metal TO-3 package. However, the transistor itself is in a round metal package, and the metal flange is separate, and holds down the transistor. Soviet electronics is like an alternate universe where things are similar but also unexpectedly different. (Vintage IBM electronics has the same feel.)