Danish FTLF M/51 L field telephone | Felttelefon (FTLF) M/51 L.
The M/51 L field telephone was introduced in 1951. It was not meant to replace the existing stocks of field telephones, but was meant to supplement the dwindling stocks of old Swedish field phones (brought home by the brigade in Sweden after WWII), old German WWII field phones, US WWII field phones and British WWII field phones. There was even some of the old Danish pre-war field phones in use.
The Danish army did not standardized the field phones before 1958, when the new FTLF M/58 was introduced. The Home Guard however, continued to use all the different models from before 1958 for decades.
The M/51 L were made by the Swedish phone company Ericsson in Stockholm, or at least the internal components. The L at the end of the designation indicates that this phone were carried in a Leather carrier, as opposed to the Bakelite / steel carriers most of the other field phones used at the time.
The phone had a "normal" hand-mic like any normal phone of the day, and a single ear phone. The 1966 manual on the M/51 states, that the ear phone is to be used in an environment with lots of battle noises - e.g. artillery.
According to the manual, it was possible to connect four individual telephones together with the M/51, and the unit could work as a small switchboard between the other four phones.
My telephone is still in working order.