How old is a forehand rifle serial no 172906?

Forehand and Wadsworth was established in 1871 and in 1890 the name was changed to Forehand Arms Company. In 1902 Forehand was taken over by Hopkins & Allen who continued to manufacture many of the same models, changing only the markings. Hopkins & Allen went out of business in 1916. It is not likely that the exact date of your firearm can be established- sorry.