This is the brass air valve found behind the trigger.
Anest Iwata Air valve seat assy 93843530 WS-400 LS-400 W-400 LPH-400 and more
Anest Iwata Air valve seat assy 93001640 KIWAMI4 WIDER4 KIWAMI-1 WIDER1 WIDER2
Anest Iwata Air valve seat assy 93001790 KIWAMI4 WIDER4 KIWAMI-1 WIDER1 WIDER2
Iwata Air Valve Shaft 93935430
Iwata Air Valve Spring LS400 WS400 LPH400 93719530
ANEST IWATA Air gauge for spray gun air regulator Air adjustment valve ES