The visual system deployed by the military seems familiar enough—there are sergeant’s stripes, general’s stars. But as Trevor Paglen demonstrates in his fascinating book I Could Tell You but Then You Would Have to Be Destroyed by Me, there’s a whole separate universe of signifiers associated with covert military activities. At first, these struck him as little more than unremarkable mementos—until he figured out that their visual language actually conveyed meaning. Take the badge associated with the Special Projects Flight Test Squadron, a highly secretive part of the U.S. Air Force that works with experimental aircraft. It’s not known how many people belong to the unit, or when exactly it began, but its emblem offers some clues about its history.

THE SIGMA The sigma symbol in the wizard’s right hand refers to the zero-visibility goal of stealth air projects.

STARS The stars to the left of the wizard figure (apparently the squadron’s principal mascot) are arranged in a group of five with one outlier. They allude to Area 51, its Nevada base.

THE HILT The sword references a specific project that was later declassified: the Boeing-made “Bird of Prey,” which pioneered stealth technology that has since been applied to combat drones and other aircraft. Images of the plane made public years later revealed its unusual shape—one strikingly similar to the sword’s handle.

Rob Walker writes for Design Observer and is co-editor of the book Significant Objects.