Originally Posted by D W
Not knowing what axles you have it's hard to tell. One way is to pull a brake drum and look for a cable anchoring the primary shoe to the secondary shoe. The other way is to pop off the adjusting plugs in the back of the backing plate and shine a flashlight in to check to see if there is a "pawl" lever engaging the star wheel adjuster. This would indicate self adjusting or "Never Adjust" brakes. Manual adjusting brakes should probably be checked annually at a minimum.
A simpler way, not requiring the removal of a drum is to merely look at the axle. Usually there is a sticker on the back side of the axle that will say Nev-R-Adjust if the brakes are self adjusting.
If no sticker than pulling the drum is the way to go unless one wants to try and peek inside an adjustment port and look at the adjustment wheel.
Self adjusting wheel (inside) will have lots of notches and manual adjusting wheel (inside) will have fewer, widely spaced, notches looking more like a "star".
Look for sticker first. Much easier