unusual vintage egg poacher, flat top aluminum cooker for campfire?

We've never seen an egg poacher like this one, and have been speculating on the idea behind the flat top handle-less lid, very inconvenient in the kitchen, but possibly very handy for cowboy style cookery! You could heap coals from a campfire right on top of this pan, I think - though we haven't tried it out.

The pan is unmarked, and is made to hold four eggs. The handle is worn and slightly loose - it's made of wood, so we'd guess this pan is probably 1930s vintage.