The Forum needs more info to better identify your .357 Magnum, i.e. s/n. Do you have the original box, tools, and paperwork? What type of stocks (grips) are on the revolver? The Model 27-2 with 5" bbl. is a popular and valuable revolver, and the German proof stamps shouldn't hurt the value much, if at all. The 27-2 was introduced in 1961 and was produced until 1982 when the 27-3 was released. Since your revolver has an S-prefix s/n, it dates to sometime between 1961 and 1969 (when S&W changed to N-prefix s/n's). If it's in really nice condition and has its original stocks (probably diamond center Magna walnut stocks), your 27-2 could easily be worth $1500+. The original box and goodies could easily add $150+.