I have a memory of T. Rex, doing "Get it On (Bang a Gong)", in front of a wall of those amps. But I can't find a pic or vid to support that. Then again, I was around 13 - 14 at the time.
Plush amps had the same vinyl-upholstered look, only with button tufting instead of the rolls.
When I saw Jeff Beck in '75 (the Blow By Blow tour) he was running two Marshall heads through two blue metallic padded 4x12 cabs.
90% sure they were Plush - haven't seen any other amps with that type of padded covering.