Tiffin pots. I've seen them on a telly programme before, but can't remember which ones. I don't think they'd have a bushcraft use, but am fully prepared to correct this.
They're used in India, where all the wives make up the husbands hot packed lunch in them. They're then delivered all over by people called Tiffin Wallahs in one of the most efficient delivery services worldwide! I remember being amazed when I saw it, just wish I could remember what it was.
If I find a reference, I'll post it.
Here ya go:
http://en.wikipedia.org/wiki/Dabbawala
Reading that, it was probably a BBC documentary I watched. Amazing reading - most of the wallahs are iliterate and there is only one mistake in every 6,000,000 deliveries. If only Royal Mail.....