Hmmm, my 6" 17 is stamped Mod 17-4. It's an AFBXXXX. I bought it new but I don't recall the year. IIRC that was a period when Smith's quality was lacking. I had to send it back shortly after purchase. They rebarreled it. The only problem is the blueing on the replacement barrel is much nicer that the original blueing on the rest of the gun ever was. All blueing is still in excellent condition but what they did on the barrel is a couple of grades better.