Locks at Bethabara 1750 - 65 . . . very, very few.
First Brethren arrived at what would become Bethabara in late 1753, and first locksmith Andreas Betz arrived fall 1754. Betz had previously served several stints repairing guns for the Natives at Shamokin earlier, and worked as locksmith in Bethlehem. Bethabara asked to begin making guns in 1759, though very few were made in first several years. Valentin Beck - gunstocker arrived at Bethabara in late 1764. So very few guns were stocked up there before 1765. Repair work may have been common, including repair or replacement of locks? 1750 - 65 provides little info for study.
As Rich says, they used whatever was available. Germanic gunsmiths don't appear to have insisted on Germanic locks - the Bethlehem and C's Spring shops had English and German locks and barrels on hand, and the quality and cost of locks varied considerably. The Wachovia wagon made regular trips from Bethlehem through Reading Town, Lancaster and down to NC - and could have taken any components, or picked up same at Lancaster. Bethabara and Salem later had trade with Charles Town. The rifle Rich mentions is dated 1775 - during the War and embargo, any lock was valuable and was grabbed up.
So if you pick a year, any lock made before that date would probably be right. The "Germanic locks in PA and English locks in South" is over simplistic, not supported by study. English style locks soon became common in PA - perhaps because so many were imported.