If you have Campbell's book, you can look at pictures of the different Winders.  The first model was a 2 band and I believe they were still leaf springs from 1905 to 1911. About 1910 is where the takedown models started and they had to be coil spring. Second model 1 band is probably during the transition where the change from leaf to coil took place. Serial #'s are iffy at best in most publications during this time.  If the metal is still in good shape, look carefully at the polish marks where the tang fits. You should see where they blend together along the seam. I think Bert Hartman is the best authority on dates and serial #'s. He occaisonally drops in here once in a while.  Maybe he'll post.  Bob