Another grafonola question

[DanP58]

Good morning
I have another question about my Columbia Grafonola. I got a couple different answers to my first question about the cup like washers I found inside the machine . Know does anyone know what the purpose of these 2 grommets on the back of the machine . I think they’re brass ( at some type metal) with three prongs/claws . Any help would be great appreciated
Dan