Correct

email (option): robmiller11(a)yahoo.co.uk

Do you think it's aeronautical ? There weren't many 12mm plugs in use on vehicles at that time. De Havilland Gipsy engines used 12mm during the 1930s.

Have you come across the YA code before ?

Could be, also some generators used small plugs? Could YA 1944 be the part number? what was "YA"? "FA" was tools, "ZA" was signals supplies.

Rob

email (option): robmiller11(a)yahoo.co.uk

As a collector of pre-war KLG Detachers, I have to say that it's a very nice thing. Is it mounted on an oak block ?