The bottom line is even though I am approaching a rather "experienced" age, I wasn't around in the 20's-30's-40's, not many shooters used chronographs or other technical marvels of the like back then, so I could not say what they loaded standard .38 spl. to in that era. I have heard the accounts attributed to Old Fuff and dfarriswheel many times and my respect for those two wise men is immense. I believe they are right FAR more often than they are wrong. I have also heard Mr. Hawks version and I cannot contest or verify either account with any authority. Perhaps if I saw something like a Lyman's loading manual of the era before +P that would constitute something like solid impartial evidence, and it would not change my current practices one whit. More of an intellectual curiosity.
I view it in the applications that I am willing to employ as a question of accelerated wear. Assuming a good Smith or similar quality revolver is good for several lifetimes of normal use at SAAMI standard pressure (a good assumption with reasonable care I think),
considerable use of +P in something like a Mod 10 might remove one lifetime. A matter of complete indifference to me.
I do for revolvers like the D Frame Colt DS agree that +P use should be limited (Colt suggests returning to the factory for inspection and possible repair every 3,000 rounds of +P) and for those that the manufacturer or age/condition dictates, none at all.
For the Mod 10 every shot results in some degree of wear, +P more wear than standard. Lots of revolvers shrug that off as a practical matter, the Mod 10 included by my observation.
P.S. Undoubtedly the most significant advancement that Smith made in producing revolvers that withstand higher pressures without catastrophic failure (bursting cylinders) was the introduction of heat treated cylinders. That occurred about 1921.
Not to mention that +P ammo was being used for years before +P was being roll marked on the side of barrels with no ill effects to the guns
