A Trappist beer is a beer brewed by or under control of Trappist monks. Of the world's 171 Trappist monasteries (as of April 2005), seven produce beer (six in Belgium and one in the Netherlands). Only these seven breweries are authorized to label their beers with the Authentic Trappist Product logo that indicates a compliance to various rules edicted by the International Trappist Association.

Brewery	Location	Year Opened	Annual Production (2004)
Bières de Chimay		1863	123,000 hL
Brasserie d'Orval		1931	45,000 hL
Brasserie de Rochefort		1899	18,000 hL
Brouwerij der Trappisten van Westmalle		1836	120,000 hL
Brouwerij Westvleteren		1838	4,750 hL
Brouwerij der Sint-Benedictusabdij de Achelse Kluis		1998	4,500 hL
Brouwerij de Koningshoeven		1884	145,000 hL

The fifth on the list above, Westvletern, produces what is recognized on BA as the best beer in the world, Westvletern 12º.    A true beer purist would only drink 12º purchased directly from the monks in Belgium, afterall, that is the only way it can be purchased (there are no resellers/distributors).  

When making an order now, the type and quantity of beer for sale are revealed. Sales are limited to one order a month per person per license plate and phone number. Also, the beer must be reserved on their "beerphone" (+32 (0)70 21 00 45) beforehand. The monks will never sell you any beer if you just drive up to the abbey hoping to get some. The reason for this is to eliminate commercial reselling, and hence give all visitors a chance to buy some.

 I'd love to make a trip over to the monastary, but I don't see that happening anytime soon.  There are individuals (that the monks would never sell to if they were able to identify them) that do sell it online for a healthy profit.   Today, I made the purchase from an individual in Belgium - a 6 pack of 12º, which will likely be split among some friends.   I'll make a blog post with pictures when it arrives!