In fact, it's a wine-tasting cup, an ancient tasting tool called a "Tastevin," which is pronounced "Taht-vahN" with a nasal French ending and means, well, "taste wine."
It's actually quite a historic item. Two hundred years or more ago, cellarmasters in Burgundy in France (where a very high-level wine society is called the Confrérie des Chevaliers du Tastevin) developed this cup to sample wine down in the cellar where it was dark, lit only by candles. The angular nooks and crannies in the shiny silver cup are designed to catch and reflect the light to make it easier to check the color and clarity of the wine.
In these days of electric light, it's no longer necessary to do this, and the tastevin has very little practical purpose any more. But it remains in use as a traditional "badge" for the sommelier, and a number of wine-accessory shops actually sell them for wine lovers who want a little piece of history for their own collection.
I doubt that anybody uses them to drink out of any more, although I did visit a winery in Georgia a few years ago that used an aluminum version for guests in the tasting room. I didn't like it at all ... too small and shallow, and the metallic cup made the wine seem to taste funny.
If you've just got to have one, though, I found three online shops that sell them to wine lovers. Artisans on the Web wine accessories, http://aoweb.com/frameset.html, has three, ranging from $17.99 for a plain silver cup to $20.99 for a tastevin with ribbon set and $22.50 for a tastevin with chain set (pictured). Wine Enthusiast, http://www.wineenthusiast.com, offers a cup and chain for $24.95. And in the UK, Waiter's Friend, http://www.waitersfriend.co.uk/gift.htm offers a tastevin for £9.50.
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