Okay, this example is not for a trailer axle, but my old 97 F150 that had rear drum brakes that were self adjusting... ;)
I could turn the star wheel in either direction to set them.. You could feel and hear the clicking of the spring loaded cable that was set to turn the star wheel in the 'tighter' direction when backing up and applying the brakes..
They worked fine, but did require adjustment when replacing the shoes.. And then some fine tuning afterward.
I don't think there would be anyway of telling if that cable/adjusting lever are present by looking thru the adjusting hole?? I could barely see the start wheel on mine..
On my TT, it has the same exact star wheel as the truck had.. Just no cable or adjusting lever to spin it 'automatically'..
Good luck!
Mitch