When pistols were sent to an arsenal or depot as unserviceable, the instructions were "throw slides in pile A, throw frames in pile B". Each part was then inspected so see if it was serviceable and could be used in a rebuilt pistol, or was unserviceable, and was to be discarded.
They then re-assembled the serviceable parts into pistols and shipped them out to the troops.
No one, repeat no one, cared if a Remington Rand slide went on a Colt frame, or if an Ithaca slide stop went into a Singer pistol. To the depot folks, a rifle or a pistol was a means of killing the country's enemies and they didn't give a rodent's rear end about collectors who wouldn't be born for 40 years.
Jim