Its the Baghdad Battery. http://en.wikipedia.org/wiki/Baghdad_Battery
I'll pass my turn. I just posted a puzzle less than 24 hours ago, so someone else can take a go.Ding, Ding
It should not be too difficult for some on this forum
I have one of those.
Indeed, and this excellent article by Richard Binder explains how to replace a fountain pen sac: http://www.pentrace.net/article012901050.html