I was using little brass General Tools caliper cause it was the only one I had metric.

Dial caliper sez .547"

9/16" = .5625"
14mm = .551"
pedal = .547"

HW store didn't have anything 9/16-20, nor 14mm - 1.25, but I was able to find a bolt in a diferent dia. w/ 1.25 thread, and it lined up fine by eye (yes I took the RH pedal to the HW store). Really looks like 14mm with L & R markings.

Found a faint "FIRST" logo on the spindle. I'm guessing First Components in Taichung. It's marked 3T and Boron and First, don't know why they wouldn't have added one more stamp to make clear which taper it is.

I'll find a known 9/16-20 or 14mm crank to try the pedal on and see if it fits.