Genuine pearl grips were seldom, if ever backed with another material.
I know the ones on that Colt aren't. They feel heavy and solid actually. You can see growth rings, and feel the rough texture on the backside. No idea who made them, or how old they are, but I doubt they came on the gun.
I probably would never have bought that gun, but my wife saw those grips and fell in love with it. It is very elegant. I'll bet it really looked sharp "back in the day" before the finish got scratched up and all.