IIRC, a round limit was never in place for production division as it was envisioned. You were supposed to be able to fill the mag(s) that came from factory as is. But as with all things competitive a race began where manufacturers started manufacturing higher cap magazines. I believe the last one was Sig offering a 21 or 20 something capacity magazine.Idk where uspsa got 10, and IPSC got 15 from but the intent was to level the capacity field.
You're wrong on USPSA -- the ten round limit in production and L10 was a result of the ten round Federal capacity limit on newly manufactured magazines at the time the divisions were introduced....
IPSC started out unlimited, had a bit of an arms race, and then decided to do something about it, but decided to cap things at 15 rounds....
That would make sense. So when exactly production division was in place? All I could find was wiki which noted nationals production in 2002 I believe. I'm sure it started way earlier than that.