I believe Chevy offered the USA-1 plates from 1969-71. These original plates had raised USA-1 (just like a real plate), metallic red and blue paint with round holes for the fasteners, and had brushed aluminum around the edge of the plate and letters. The aftermarket style plate has an all white background, the fastener holes are oblong, and the entire plate is flat.
I have the aftermarket plates. Call me cheap, but the "originals" (NOS) are around $50 - opposed to the whopping $8 I spent on mine!
WOW, are dealerships shady or what!! $50 for a license plate??? I bought one like in steelblue75's avatar in the late '70s for like 2 bucks. A friend of mine got one just like it for his truck last year from a Chevy parts catalog for $6.95, even showed me the mag. And yes, it is raised.
Back in 76, i bought a 78 vette and the dealer gave me a USA-1 plate with it. i no longer have the vette, but i still have the plate. i resently bought a plate from Ecklers or Corvette America, that looks similar, raised letters and all