The IRS says this downtown sign was snapped in half by high winds. (Dan Zak/THE WASHINGTON POST)

The facts: A sign outside the Internal Revenue Service headquarters was beheaded last month.

The hypothesis: A District resident, furious about paying federal taxes while being denied equal representation in Congress, took a sledgehammer to a small symbol of America’s most mind-boggling constitutional inconsistency.

The official IRS response: The wind did it.

You know the sign. Or you know the type. If you work for or near a federal agency, you see them everywhere downtown: The signs are thin and 10 feet tall, with a slight convex curve toward their tops, like a legion of shadowy soldiers with poor posture. White lettering spells out the agency name on a black surface bleached by the sun. The official name for them is “molded fiberglass monolithic facility identification signs” and they were installed around the city in the mid-to-late-’70s.

They look bland and procedural and definitely of the post-Watergate era. And they look and feel sturdy. Like it would take a hurricane to snap one in half. Winds did reach 65 mph on Feb. 25 in the D.C. area, and the IRS says it has security footage of the ensuing decapitation-by-Mother Nature at the southwest corner of 12th Street and Constitution Avenue NW.

They will not show the footage to us.

Engineering professors at the universities of Maryland and Virginia say that wind cannot be ruled out as a culprit.

The hypothesis persists. A visual hiccup in the federal facade and the approaching specter of Tax Day are reasons enough for conspiracy theorizing.

“Vandalism,” says Russell McInturff, who was visiting from Lubbock, Tex., a couple of weeks ago, as he passed the sign.

Vandalism, agrees the rest of his family as they wait for the light to change at 12th and Constitution.

Why vandalism?

“Because it’s the IRS.”

The agency is no stranger to threats and injury.

But perhaps we’re letting our imagination run away with itself. No one was hurt at 12th and Constitution. It’s just a sign. An ugly sign, at that. The damage is actually an improvement — it reveals a far more interesting interior of plywood and honeycombed cardboard and a strange fibrous membrane that feels like horsehair.

Who’s even responsible for these signs?

A man named David Pesanelli. He’s 73. He lives in Rockville.

In the ’70s, he sketched the curved design on a cocktail napkin. He thought it was more graceful than the usual vertical slabs that were plunked in front of buildings in the Washington area. His design firm refined the concept for use outside the former Psychiatric Institutes of America on MacArthur Boulevard NW. Within a year, he noticed a “poor interpretation” of his design on display outside federal buildings downtown.

“I was kind of horrified when I saw it,” says Pesanelli, who closed his firm in the late ’80s and has been a communications and environment consultant since. The company that manufactured the signs on MacArthur Boulevard had co-opted his unpatented concept for its federal contract.

The result, in his opinion, was a more rigid, brutalist version of his initial notion. And they popped up all around town.

“Some of the buildings themselves are kind of brutal,” Pesanelli says. “They’re massive, clunky, and they’re projecting all kinds of imagery of overweening power. In a funny way, they may be a fairly appropriate match for the buildings.”

But no match for a gust of wind. Or a sledgehammer, if you’re a romantic.