Leave it to the brewery that claims to be the world’s most superannuated to bring a special present to the birthday of its longtime friend, a 500-year-old piece of parchment.

The Bayerische Staatsbrauerei Weihenstephan—better known as Weihenstephaner—has brewed a new one called 1516. Even now, a fair amount of it is on its way to the States. In Germany it will begin appearing April 23, the Reinheitsgebot anniversary, but you may see it sooner in American shops and bars.

And what type of beer is it? Well, it’s not a sour-double-imperial-session-IPA whatsit. It’s a kellerbier.

Why a kellerbier? Because it’s old-fashioned, according to Weihenstephaner technical director Mario Schäfer, who oversees the brewers.

“Because it’s an original kind of beer brewing,” he told me. “In former times they didn’t filter their beer, so they had to produce kellerbiers.”

In the days before controlled refrigeration, “kellerbier” meant simply beer obtained from the local kellers—public cellars dug into shady hillsides, where beer could be kept cool until ready for drinking. It was fresher there and often enjoyed on the spot. It would have been unfiltered, but that was not (yet) the point.

The kellerbier tradition has evolved but it continues most famously in Franconia, well north of Weihenstephan’s home in Freising. Meanwhile “kellerbier” and its cousin “zwickel”—they are effectively the same thing—have become keywords for unfiltered lagers sold across Germany, appearing even in common restaurants and supermarkets.

Some are cynical, thinly veiled versions of uninspired pils or helles with a bit of yeast left in there. The word “Naturtrüb”—naturally cloudy—is often attached, and the implications of health and nature allow you to infer what you like, so long as it helps you to rationalize buying some more beer.

But many of these commercial kellerbiers have more to say, as does the 1516. At 5.6% strength, its gets compelling character not from leftover yeast—in fact the beer is centrifuged to a precise degree, leaving only faint haze in its orange-amber color—but from an unusual combination of hops. Joining lemony-herbal Hallertauer Mittelfrüh is a rare heirloom hop called Hallertauer Record. Schäfer said that the variety has nearly disappeared—only one hectare grew last year—but he wanted its spicy character. It’s not a flashy beer meant for sipping and sampling; just a tasty one that will reward repeat drinking.

The name refers to the year Duke Wilhelm IV signed that parchment, which had more to do with keeping beer and bread prices low than it did purity. Never mind that. Many Germans are now proud of that law, decreed 35 miles north of Weihenstephan when it was still just a pup of a kitchen brewery in a monastery, only 491 years old by then. Or thereabouts.

Weihenstephan famously claims to have been brewing since 1040, citing a license granted by Bishop Otto I of Freising. However, its legitimacy is disputed, with one historian saying the document is a “clumsy forgery” from the 17th century. Also, fires and wars sometimes interrupted things.

Oh well. Who judges a brewery by its age, anyway? I prefer to go by what’s in the glass. Weihenstephan has a reputation for classical styles brewed with technical excellence; the Hefeweissbier scores a 99 on Ratebeer, while DRAFT reviewers gave the Original Helles (a.k.a. Premium) a 98.

But you are an independent drinker and can make up your own mind.

More German novelties to hunt:

Those who want to balance their Reinheitsgebot toasts with ornery impurity might consider some new entries from Freigeist. The firm is run by enthusiast Sebastian Sauer, who nurtures an obsession for forgotten German beer styles—often those stamped out by the purity law’s national adoption in the early 20th century.

Freigeist’s new ones en route to the States include: Berliner Scheisse Wildstrawberry, a sour Berliner braunbier spiked with wild strawberries and given a name best left untranslated; Poltergeist, a strong stout brewed with mussel shells in collaboration with Pizza Port and Oxbow; and two versions of Gruit Vibrations, Pale and Dark, both dosed with spice cocktails and brewed with Denmark’s Kissmeyer and Norway’s Nøgne Ø. Sauer hires the Vormann brewery in Hagen-Dahl, south of Dortmund, to bring his recipes to life.

Also from the Rhine region: The traditional altbier brewery Uerige is playing around with fresh hops. Its Jrön is a green-hopped version of its strong-alt Sticke.

I was lucky to discover the Jrön recently at a specialist pub in Berlin. Confession: I’ve never much cared for the Sticke, finding it to be a rough slog compared to (glass after lovely bitter brown glass of) Uerige’s fresh Alt. But here the Sticke’s bittersweetness is joined by deep, minty-herbal hop flavor and aroma that made it all worthwhile.

It reminded me of an unpleasant drive suddenly improved by a good audiobook, making the whole experience entertaining enough that you are surprised and disappointed when it’s suddenly over.

Some of it is headed to America too.