I've always loved crystal door knobs. The house we affectionately call "the old house," where I lived from ages 5 to 11, had door knobs just like these.
I've held onto this one for awhile and I'm not sure where I got it. I like to think it somehow came to me from "The Old House." It is possible.
Fortunately I have one door in my apartment that has these.
Apparently they became popular in World War I when the metals normally used were scarce.