What's in the Box?

[ant907]

Was digging around the scrap heap until a came across this box.Its a portable potentiometer Type 3184 D Made by H.Tinsley & Co. Ltd

The inside lid has full schematic, its a bit damaged but still quite distinguishable. The guts of it looks and smells 1940-50s maybe,

I know nothing about this unit or what it is used for, just thought someone may now something about it, Never heard of "Portable Potentiometer" until a found this.

Any information would be great.

Cheers!