You're probably aware, but there's a "Gil Boyd" on Milsurps.com who's able to check factory production records, through a former PH head armourer.
Their records aren't 100% complete (due to the way PH, was taken apart
), but often for a given serial number they can sometimes find out:
-Production date,
-Test target grouping size,
-Wether a factory supplied optic was requested, i.e S&B PM, Swaro ZFM, Tasco
-Destination & purchaser, more often than not, some branch of a Police unit in the UK or continental Europe.
-some times stock colour, & configuration info if a bit non standard
may or may not be of some interest
https://www.milsurps.com/showthread.php?t=47454