The Colt Target grips with silver medallions were made for the original Trooper, the Officer's Model Match, and the 357 model. "357 was both the name and caliber". It looks like the original Trooper). In the 1920's, Colt began installing checkered walnut grips with silver medallions on revolvers. During WWII and up to the early 50's they used brown plastic grips, also known as "Coltwood". Starting in the early 50's they went back to walnut with silver medallions. In 1955 the Python was introduced, and it was super-premium hand assembled and fitted gun. They wanted to let the consumer know that these were the top of the line revolver. So they installed the gold medallions in the grips. Gold being the premium metal and color, the Python wore those. And all other guns received silver grip medallions. And then starting some time in the 70's gold started being used on the other models on an irregular basis, and by the 80's everything had gold medallions. Then a time came when they had silver or gold depending on what they had on hand. But in the beginning, Gold Rampant Horse Medallions only!
The first model Python revolver grips were fully checkered. Those are shown in the picture.