It started with the Colt SAA in early 1890's, the SAA had a one piece frame instead of the 2 piece frame held together with the wedge. I read an article on this in one of my dad's older colt books / encyclopedias that Colt struggled to find a steel that was strong enough to take the high pressures created by smokeless powder which I believe is 3X that of black powder but was still economical enough for mass production to keep cost low. It's generally accepted that in 1900 at serial number 192000 that the SAA was certified for smokeless powder and were identified by a VP (Verified Proofed) proof mark on the left side of the trigger guard, but up to 1905 there were Colt revolvers leaving the Colt plant without the VP mark and also reports of revolvers without the VP mark being returned to Colt for warranty work and being returned to their owners with the VP mark. it was after 1905 the VP proof mark consistently appeared on every gun leaving the Colt factory.
Unfortunately my dad's collection of gun books mysteriously disappeared from the time dad passed away in Jan 2020 and my mom passing away in Aug 2020 so I cannot verify what I've written above, even the modern day Colt historical experts disagree as to when Colt fully transitioned from black powder to smokeless powder. I have seen it mentioned in several Colt SAA Forums that original Colt SAA revolvers built before 1900 be shot using only black powder loads and not smokeless powder loads due to the uncertainty of the integrity of the steel frames.
Now before anyone calls BS my dad was a huge collector of early Colt and Remington revolvers and Winchesters. I grew up living and breathing in Colt, Remington and Winchester history. Some of the early Colts dad owned included .36 Patterson, 1st, 2nd and 3rd Model Dragoons, a Walker Colt, numerous cased 1851 Navies and 1860 Armies and cased Remingtons.
It's probably for this reason I fire an original Colt 1851 Navy.
Dad passed away in January 2020 and mom passed away in Aug 2020, his gun collection was sold off years ago, he sure left one hell of an impression on me tho.
Attached in an article on dad after he retired from INCO.