Tillotson made industrial engine and outboard motor carburetors, also carbs for small engines, motorcycles, airplanes, etc. That T handle is on an adjustable main jet, and the carb was probably on some sort of commercial rig at one time. Most fleet mechanics would adjust the main jet(s) for the best performance under load, and then cut the shaft off flush with the gland nut to keep drivers from tinkering with the high speed mixture adjustments. Lots of engines have had the pistons melted out of them by drivers trying to get a bit more performance by leaning the mixture a bit and then driving full throttle for long distances.
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!
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