If the metal disk was vertical, then it was probably a Polyphon player. Unlike the pianola where the holes produce the notes, the holes in a polyphon are where metal has been bent back to form a pin-like structure. There's a link below to a short video showing how the system worked. The one in the video is horizontal, but Polyphon produced much larger vertical ones sometimes with multiple tracks, accessed by moving the disks slightly sideways.https://upload.wikimedia.org/wikipedia/commons/a/af/Polyphon_Stille_Nacht_Heilige_Nacht.webm