I know that someone here put a fancy long-name on this grip material. But to me it looks like simple hard rubber, introduced about 1860.
Hard rubber comes in two colors, black and brick red. Merwin & Hulbert attempted to mix black & red for grips, but experienced problems with duplicating the results, and scrapped the idea.
Hard rubber retains its shape, unless force and heat are applied. Black hard rubber tends to turn brown if wet and warm (like with sweaty hands). I have made black hard rubber turn brown by placing it in boiling water for a few seconds. What is lost is the black pigment at the surface.
As long as the grip screw is not tightened any more, these grips should remain as flat as they are after 71 years.
As for shooting this #93, I have no problem with that on a mere 22rf. If it was a 45 Colt, then especially on a very early production gun, the pressure and jarring might cause a problem. I know that on some very early Colt models, the factory found it necessarily to add a few 1000th to the cylinder walls. One prime example was the Colt M1877 DA, when during the 1st year 0.030" was added to the cylinder diameter.