When thinking of it, imagine the direction of the thread allowing the pedal to tighten as you ride. Or another way is that they always tighten in the forward direction. If you're asking because the bike is so old, the answer should be the same as it is on my 1912 Iver.
It's fortunate that it was the right pedal that failed. You can use a standard screw extractor to get the remaining piece out of the crank. It probably would be a good idea to change out the left pedal as well. I'd hate to think about losing a pedal while standing and pedaling up a hill.
And yes, I remember the reverse-thread lug nuts on the left side of my dad's 1963 Plymouth.