S&W stainless guns use carbon steel, casehardened hammers and triggers. Earlier guns had the hammer and trigger hard chrome plated, late guns use color casehardening.
Some model S&W revolvers, (VERY early model 60's), had stainless steel parts, but S&W decided that carbon steel would last longer.
S&W always called the early plated parts "stainless" which since hard chrome doesn't "Stain", is correct.
No 686's had real stainless steel hammers or triggers.