After reading this, I checked THE CANADIAN GUNSMITHS, 1608 to 1900, by S. James Gooding. There are two William Fishers, but no Jacob. Fisher seems to be a fairly common name among gunsmiths, I have several Fishers in Illinois and Iowa, but no Jacob. I thought the rifle might be Michigan-made, but the only Fisher listed in the Michigan book is Elam J. Fisher.