That's called a "Double D" screw head, and the only place I've seen something similar is the metering rod limit screw on an electronic control Quadrajet carburetor. A good friend machinist can make a T-handled tool for them with a piece of round stock and a correct-sized 4-flute end mill in a Brideport mill. The machine shop next door to my shop at the high school where I taught made me several Quadrajet adjusters that way. If you can get one screw out and mail it to me, I'll make you a tool.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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