Thank you for your input, TM,
Indeed, Victorin Piguet should be included in the list of specialist firms that provided chrono calibers to PP. (Although, I was inder the impression that the majority suppliers since the 1960's were Valjoux cal. 22/23 and Lemania cal 2320.)
Also, to my knowledge, PP began production of own calibers only (some years) after the Sterns bought it in 1932. (LC tried to buy, but Sterns eventually got the company.)
VC have had and still have an in-house production of the 13"' repeater movement. It was the only in-house wrist-watch movement they've had until recently. But they did have one
As to the past, going back eones: after G.-A. Leschot (a talented engineer working for VC) modernized "serial" movement production in mid-19c, VC became a supplier of pocket watch ebauches to the Swiss industry. This is well known. (Who knows, maybe PP bought ebauches from them too.)
AJ