When we are drawing up a label we refer to a specific font family (all the letters, numbers, signs etc in that font) as a type case. I understand, from Father Steve's and Wow's posts how it could have arrived at that meaning. Is this term used elsewhere?

As I understand it, yes - almost anywhere that printing is involved: advertising, journalism, publishing etc. These days I've noticed it being used to describe the entire font family - sizes, italics, bold, light etc. Typographers abhor this lax usage, but hey - if it works...