What you describe sounds exactly like this description of old French pedal threads:
https://www.sheldonbrown.com/pedals.html

So the question is really, was your crank made with optional French pedal threads? Just because Gipiemme also made cranks and pedals with English thread doesn't mean they didn't have other options. Just like Shimano still makes Italian BBs.

Does the inside of the crank have any markings, or around the pedal holes?