Stephenson:Neal:Quicksilver:422:fine golden beer from Pilsen (David C. Weichert)
From the Quicksilver Metaweb.
Golden beer from Pilsen usually refers to Pilsener Urquell, according to its own marketing department: "Das erste goldene Bier der Welt" (The world's first golden beer), see: http://www.pilsner-urquell.de/. The formula for Pilsener beer (usually called lager in English) only dates back to 1842, when a brewery in Pilsen started brewing it under the aformentioned name. Nowadays Pilsener Urquell is owned by the Southafrican multinational SAB Miller group, see: http://www.sabmiller.com/.
Pilsener is fermented using a yeast that is active between 4 and 9 degrees Celsius, this type of brewing process is called untergäriges Brauverfahren (bottom-fermented) in German. Such beers could only be produced in the winter. In the Rhine area and in other places with a milder climate beers of this style were only brewed from the late nineteenth century onwards, when refrigeration had been invented. In Bavaria however such beers had been brewed since the sixteenth century. Due to the process of malting and the quality of the water those Bavarian beers were darker and cloudier than todays Pilsener (lager).
It is highly unlikely that a "fine golden beer from Pilsen" was actually served in seventeenth century Leipzig as portrayed by Neal Stephenson. Beer was brewed in Pilsen at least from the 13th century onwards (when King Wenceslas II granted the right to brew) and by the end of the Thirty Year War (1648) the town had 26 breweries, however it was most likely not this kind of beer that was produced then.