That style of round blanking plate with the spring-action claw used to be common in Germany when I was but a wee child. The springloaded claw that would grip the inside of the wall box.
I wonder if they're still commonplace. Maybe "Texas Ranger" or "C-H" would know?
Sometimes I would pop them off the walls to play with them....don't ask. I had a facination with round lids of all sorts at that age (3-4 years old).
I remember they used to come out of the walls rather easily. Not something I'm very happy about nowadays, of course. Prefer something with screws if it's going to be reachable by a child. Guess a ceiling is no problem though.
[This message has been edited by SvenNYC (edited 08-01-2003).]