Props to Swamprat.
1912
1920
1938
1952
1974
1912

1920

1938

1952

1974

"In the days before firearms, when the crusaders went into battle on horseback and armed with spears--one very intelligent horse, seeing that his rider was about to be pierced by the enemy's spear--reared on his hind legs, grasped the spear in his mouth, struck out with one hoof and broke the spear: In heraldry, a horse signifies readiness to serve the monarch. The broken spear signifies a warrior slain in battle. By carrying the spear, this warhorse is continuing the fight for his fallen rider. The broken part of the spear is pictured in the horse's mouth and the handle through his legs. It's a fitting symbol, considering the indomitable spirit of inventor and entrepreneur Samuel Colt. This is embelmatic of the Colt--always coming to the defense of the master."Thanks, more than I imagined. Still, what do they mean, if anything? Does it matter what gun they go on? Revolver vs semi? Frame size? Same one for year across the spectrum? The shape of the eyes also changes as do the position of the forelegs. I see some changes in the tail, too. Some of the colts look a little chunkier than the others.