Antique vtg light fixture bulb cover with anti-theft triangle lock screws

Description

At first I didn't think anything of it. It didn't look particularly unusual. Old but not rare. But then I saw each screw is like a triangular clock key. I have a small collection of sockets with this device that keeps someone from being able to access and steal the bulb (back when bulbs were expensive). You need the key to wind it or a really small pair of needle nose pliers I assume could also do it. Fun early electrical survivor.