The SF VI, small frame ,v spring , improved, used a slightly different v spring ,a transfer bar ignition and slightly modified internal parts. The barrel was crowned and less tapered than the older D frames , the ejector rod head was a a cast part. The early Sf revolvers had a tendency to light strikes. That was changed on the DS2, along with a heavier firing pin spring. When I bought the 3 inch DS2 , I got it as a shooter for $239. I rounded off trigger and shot it. it was as accurate as any other D frame , I like the 3 inch barrel ,a great packing revolver that will stand up to the heaviest 38 spl loads. Regret not buying a 2 incher ,and if I had seen one , a 4 incher. I may have decreased the collector value by firing it , but I bet that 50 yrs from now , it will be worth more than $239/