This is KD-6 (Director Concentrator),

  Local communication telephone set for 6 numbers. The set also includes a power source with a signal device.

KD - Director's Concentrator - Allows the Director to connect to and switch between 6 external phone lines.

There is a trace of glue on the disk, where the Russian symbol, a pentagon, has been.

Unfortunately, I don't know the working order.

Weight about 9 kg.