*UPDATE*
I am learning, little by little. These are SIDE PULL BRAKES. Which might explain the missing centering adjust screw. So...
Only the right side engages, the left side sits. Is the adjust supposed to hold the end of the cable/housing securely? This pulls out to reveal cable as I squeeze the calipers. With this new information the Park website concerning Side Pull Brakes seems relevant. But any advice is greatly appreciated.