They were little 1" x 3/4" (approximately) switches that you slipped into a metal bracket and used a small blade screwdriver to bend a retaining tab into the frame of the switch. I have one wall outlet, with 3 of those little switches. don't think they are made anymore and it would be a pain to change them out to newer.
But...reason I'm searching is I need a brass switch plate to cover them. the standard 4.5" x 2.75" plate with those 3 little holes. The plate would be mounted horizontally, the 3 switches would be vertical.
I've searched the fancy cover plate sites with no joy.
All the covers in the house are shiny brass except for this old cheap plastic cover that customer wants to replace.