I have a 4 digit Centennial that I bought used in the 60s and the grips had been changed to checkered grips. The grip safety was a problem. If I remember correctly there is a piece inside the grip that the outside piece pushes against and I removed that inside piece. I didn't know anything about pinning the outside piece. Even if the grip safety doesn't work it's still as safe to carry as any DA revolver and it's been carried many miles in my front pocket. Larry