When it comes to wines, I rarely have any clue what I'm talking about (other than the fact that a corkscrew power tool is the best idea ever, of course). Chances are, your friends who claim to be wine experts don't either. In case they still insist they can qualify as a personal sommelier without batting an eyelash, you can test them with this: a Vintage Wine Disk that quickly tells you a particular bottle's rating.
Made by silversmith Christofle, the shiny cheat sheet is made up of two concentric disks that you spin to find the rating for a specific wine from a specific year. Ratings are taken from "Guide Hachette des Vins," the annual publication highly regarded as an authoritative source for French wines.
Since there's limited space on the silver-plated disks, the Christofle Vintage Disk only includes information for some of the more popular bottles. Ratings (between 1 to 20) for eight vintages (Alsace, Bordeaux Liquoreoux, Bourgogne Blanc, Loire Rouge, Cotes du Rhone, Sud-Ouest Rouge, Bourgogne Rouge and Bordeaux Rouge) from 28 years (from 1945 to 2007 -- it skips some years) are carved into the discs.
The outer disk measures five inches, so you can easily hide it in a bag while trying to put one over on your "cultured" mates. Since the disk is flat, it can be used as a bottle coaster, too -- I'd discourage it, however, since you can't use the thing with a vino sitting on top.
Another reason not to use the Christofle Vintage Disk as a coaster: it costs $322. Hey, nobody said pretending no know your wines won't cost you.