['68OrangeSunshine]

Here's my guess: I am a Stagehand. Had my card for 28 years. Besides legitimate theater, touring shows, operas, ballets and rock 'n roll, we also do exposition work at trade shows. Not just setting up the boothes, tables and carpet, but also installing displays in certain clients' boothes.
Sometimes we get to take home stuff the client
wants to discard after the event. It's called "swag" in the trade.
My guess is there was a big auto show in Vegas [in the late '60s] and the wooden mockup for the "New Breed Truck" was in the booth. When the show was over the clients [GMC, Chevy?] didn't want to ship the bed back to Detroit, so they told the stage hands to tip it in the dumpster, and caught a plane out of town. But one of the locals had a better idea and swagged it...
Mystery over.