This is a sideswiper (cootie key) KDM by Experimental plant of LMNIIP* USSR.

Two modifications were released. These are KDM-1 and KDM-2. Mainly they were units of the shipboard radio set “Ersh” (it is ruff in English) and others. These keys were popular among radio officers and at The Soviet Polar Stations.

This photo shows the KDM-1.

* – The abbreviation LMNIIP stands for Leningrad branch of the State Design, Survey and Research Institute of Marine Transport.