A Y-shaped bit

[ianr]

My Pifco clip-on fan has stopped twirling after thirty years. Can anyone lend me a Y-shaped bit so that I can open it up and tend to it? See attached pic. The circular recess is 8mm diameter, so we're talking about a domed screw with a head diameter of ~4-5mm. Its slots are actually deeper and seem in better condition than the photo suggests.

[handymaneast dulwich]

You need a tri wing screwdriver been many years since i have seen a screw like that.