Ammo works too. Worked at a shop where they would have us transport a 1U server in a case that also held a single .22 round. You would fly to the location, pic

Ammo works too. Worked at a shop where they would have us transport a 1U server in a case that also held a single .22 round. You would fly to the location, pick up the server, and hand the bullet to the person working the desk to discard. Got the occasional dirty look, but prototypes were never lost. Empty case could be checked on the way home.