Didn't S&W make the medallions out of plastic for a time?
I'm not familiar with the era and grip type(s) they were used on If there were specific ones, and it may not be the case here at all.
But if they are plastic it's a good chance soaking in acetone will make them into a blob of goo.
Acetone does that to many plastics.
Otherwise, if they are metal ones, acetone or even lacquer thinner soak will generally remove the stuff. Some people refinish them with shellac too. That's available as a spray finish now as well and can be applied evenly and quickly. It too can chip, can craze and even get soft if built up to much and then exposed to some heat.
Spray laq or poly work well for built up finish. Some of the poly is quick drying as well.
Use very thin coats.