German Vehicle Driver's Foot Heating System

German Vehicle Driver's Foot Heating System. Marked 'Größe 42' indicating the shoe size. Complete with cable and bakelite (car type) plug. The set is not visible maker marked or dated, I don't know exactly from which period this set date, production and materials look to be from WW2 period. I've never seen a similar set before and can't find any information so any information is welcome. Priced accordingly in my opinion!