Asked and answered.
At least 20 years ago, someone (Dean Grennell?) did an article for the
Gun Digest Annual about making a 1911-type fire accidentally. He and his pals conducted some tests and decided that a GI .45 with noticible wear and tear WOULD fire if dropped from some great height, landing on a concrete floor, directly onto the muzzle. This would overcome the inertial of the standard firing pin and the resistance of an older spring, and impact the primer with sufficient force to fire the cartridge.
I wish I had a copy of that article at hand. I BELIEVE the required drop distance was 17 feet, but it MAY have been 27.
It is noted that the chance of such a discharge seriously hurting anyone is small, as the bullet would exit the muzzle pointed straight down, with little ricochet potential.
Colt's installed the Schwartz firing pin safety on a relatively few pistols during a time when many users still carried them with the hammer down. This was an attempt to keep them from firing IF the hammer slipped from under the thumb,
after the sear was disengaged from the hammer notches, and also
after the trigger had been released. Colt's soon decided that this feature was really not needed, and it increased both complexity AND the cost of production. (Exactly as the similar features do today, but there are more litigators involved in firearms design and production now than a few generatons ago.
)
Best,
Johnny