I believe the N in a triangle , on the grip frame , indicates the original S&W factory finish is / was nickel ... see post #2 for the factory
re-finish mark ... R-N in a rectangle .
Gary
While the Factory did routinely stamp a refinished gun, they did sometimes neglect to do so for one reason or another (possibly just an oversight). So lacking a refinishing mark is not 100% proof positive it was never refinished. Just saying.......