What is it?

Ok folks, I have a question.   My sister found this at an estate sale and we have no idea what it is.  Any idea?

It's made of brass and stands 4" high and has a 3" diameter...

It says "LUSO" and is made in Portugal....

I can't even begin to guess what it is.

Help me out!

**UPDATE - Thanks for all the interesting guesses, but I think my friend Della over on FB had the best idea - an antique ink pot.   What do you think?