I was an armorer in the Army for 9 years. During that time, all our sidearms were 1911s made between 1942 and 1945. I had a serial number sheet showing when and by which company all the guns were made. It was common to find slides from one manufacturer on a frame from another. Finding any gun that looked original was rare and probably a coincidence. A frame might be from Remington and have a Remington slide, but odds are that slide hadn’t shipped with that frame.
The 1911 I used in Army competition was a bit odd. The serial number was SM11131. The SM was for “Service Match”, meaning the gun started as a .22 and was switched to .45 in a depot rebuild at some point. That gun was quite accurate, very reliable and shot right on the sights for me. I won my first “LEG” points with it.
Sadly, all those great guns were probably destroyed after the switch to the M9.