No, it's steel, and I carried it out of the store in 1970. I had to carry it for my mom, it was her gun, she signed for it....(grin)
It is thin, has something like a diamond-plate pattern on it, a magnet sticks to it, and the bluing has worn off the edges.
I never paid much attention until just a little bit later I started seeing them with the plastic buttplates. I'm thinking they just used up old stock before they started installing the newer ones.
