Ladies and Gentlemen, this is not a prop from Phryne Fisher’s Murder Mysteries (I am ADDICTED to that show now): this is an actual 19th century ring pistol.
The item description is as follows: “Manufactured circa 1870. Made for use by ladies, this ring gun was designed to fit on the small finger. This is a pinfire ring revolver which measures 1 3/8″ in total length. It has a 5/16”, six round smooth bore cylinder, approximately .06 caliber pinfire operating on the pepperbox principle without a barrel. There is a tiny hammer cocked by the fingernail and then the trigger is pushed inward to fire. The ring portion is German silver and marked “FEMME FATALE” and engraved with a simple leaf pattern and the remaining parts are a bright niter blue. Complete in a blue leatherette case with a gold embossed wire border around the outer edge of the lid, a German silver inlay marked “FEMME / FATALE” in the center and blue and purple satin and velvet lined interior French cut to accommodate the ring, a tiny screwdriver/wire brush and six pinfire rounds.”
Further pictures at this site.
All I can say is: I HAVE A MIGHTY NEED.
The Victorianachronists 
All I can say is: Weapons like this are forbidden today. Like the sword hidden in a cane, they are stealth weapons, hidden – which makes them extra dangerous. Of course – the small size of the ammunition makes sure this is not a life’s danger.
And I doubt that such a “weapon” could really impress somebody threatening you – unless you fire directly into the eyes or .. some place very sensitive … ahem …
Oh, for sure it’s highly illegal to carry concealed weapons like this. It’s still pretty darn awesome, and would certainly do some damage in close quarters.
Would hurt, yes..
and that would be good enough, wouldn’t it?
Would it pierce through the skin? I doubt it …
I think I would stay with a pen-pistol – that shoots of darts with the same drug that the “date drug” is from … but of course that is a matter of taste. I am totally non-romantical and prefer efficiency.