Those brakes predate the self adjusting style. The notches of the star wheel are retained by contact with the spring across the top, so no lock is needed. There should be an oval slot in the backing plate behind the star wheel that allows a big screwdriver or a bent "brake adjusting spoon" to be inserted to do the adjusting. The adjustment procedure is as follows- - - -tighten the brakes against the drum until a firm drag is felt- - - -not completely locked up- - - -by turning the tire. Then back off 10 notches of the star wheel. DO NOT listen to advice like "back off until the wheel turns freely"or "Keep backing off on the adjustment until no drag is heard/felt- - - -both those statements are made by people who don't understand the operation of Bendix brakes. Since the brake shoes float free at the bottom, there is no way to feel when the shoes are backed off far enough- - - -particularly since one shoe is likely to stay slightly in contact with the drum no matter how far the adjuster is backed off. 10 clicks on a starwheel with coarse teeth is one turn- - - - -20 clicks for a fine-tooth self adjuster wheel gives the same 1-turn adjustment. The shoes self-center in the drum when the pressure of the wheel cylinder pushes them out against the drum.
You'll need to remove those adjusters and free them up with penetrating oil and/or a little heat, then use high temperature grease like disc brake wheel bearing grease (sparingly) to lubricate the threads. There's a very thin spring washer between the adjuster body and one end of the adjuster where it meets the brake shoe.
Jerry
