This is an S10 model, which Stihl informs us was produced between 1968 & 1973. Andreas Stihl made his first (electric) chain saw in 1926, which may be the first chain saw of all.
Stihl lost ground to the U.S. manufacturers in this country during the Second World War, but now that it is imported again is one of the leading brands. In fact, Stihl claims to be the largest producer of chain saws in the world today. (Thanks to Viking Lumber Co.)