Condolences on the loss of your parents.
I've read that when the Russians put their captured handguns in storage, they removed the grips and then put the guns in barrels of oil to preserve them. I don't know if it's true but it would explain why the Russian capture guns often have grips on them that were not on them originally.
WRT your Colt .22 pistol. They did not make a Huntsman in 1920. They made a Target Pistol that was later renamed "The Woodsman" in 1927. Those made from 1915 to the name change in 1927 are now called "Pre-Woodsman" pistol. The serial number range for 1920 is 20200 ~ 24999 approximately.
If, as I suspect, there is an oval in the back of the Colt's grip with checkering then ONLY use standard velocity cartridges. The main spring housings on those with the checkered oval were not hardened and hi-velocity cartridges will damage the gun. Colt, for a time, offered replacement MS housings with parallel horizontal lines on it that were hardened and OK with Hi-Velocity cartridges. See picture below.
