Smith & Wesson N frame thumb piece nut, blue $10.00 Part 21 on the exploded diagram. Used, excellent condition blue thumb piece nut from a Model 57, N frame revolver. Will fit other models of N frame revolvers. In stock Smith & Wesson N frame thumb piece nut, blue quantity Add to cart Category: Smith & Wesson Related products LPA Smith & Wesson M&P Fibre Optic Adjustable Sight Set. $195.00 Smith & Wesson K frame mainspring $15.00