I have a book the Longriffles of Pennsylvania. By Russell Harriger. About the gun makers in Jefferson, Clarion and Elk counties.
This book has a section on family member Christina Huff (Mills) Information about Isaac Mils Says that Joesph was Isaac's father who remarried to Christina Huff. and that she had a daughter from a previous marraige. Lots of information on Isaac.
I can email the pages to anyone who would like them.