AFB Carburetor Question

Pretty sure that large screw is idle air bypass. It is rt. hand thread. Those carbs that had left hand thread screws that I have seen are AVS carbs, not AFB & the screw is near the top, not the bottom of the carb. Head of the screw is normal size, not enlarged.
My GTO uses the same type of AFB carb, does NOT have an idle speed screw on the driver's side of the carb body, although the casting is there.
The large centre screw adjusts the idle speed & outer screws trim the idle mixture. These carbs usually have thick[er] pri t/blades with machined sections.