Not for the B-21 Bomber, but a still active project LRSB-D, or Long Range Strike Bomber- Demonstrator.

Rare USAF Joint Program Office challenge coin for a CONFIDENTIAL Airframe where Lockheed Skunk Works and Boeing Phanom Works are spear-heading the Joint effort "INVISUS CUM LIBERTIAS ET INSTITIA OMNIBUS" translates to "ATTENDED WITH LIBERTY AND JUSTICE TO ALL" .

Nothing to do with the 21

Lo observables, Flight Test, AFLCMC WAG. SPECIAL PROJECTS stealth

Stealth, Lo Observables, Flight Test Area 51, Tonopah Test Range, Air Force