if i'm not mistaken, those are bakelite grips.
bakelite is a sort of pre-plastic, plastic. your early 50s kitchen knife handles, for instance.
i have a 1938 detective special which had those grips on it and they were loose, bad loose. got the gun for a mere $250 b/c the guy bitched about the grips and how he couldn't get 'em tight enough.
if they're exposed to heat repeatedly, the grips will shrink and alter their fit. those original grips may hold some collector value with your pistol, but if they don't fit and lockup correctly, operationally, they're junk to me. i like the ivory grips personally, and only about 40 skillion people out there make custom colt auto grips.
FWIW, i found an identical set of new, in the box, never been installed, still wrapped in wax paper with $6.00 price tag visible on the box, identical set of grips at the very next gun show for the detective special. $30 and i was on my way to the house to swap 'em out.
either way, you have an outstanding pistol there. really, really cool.