After years of collecting, research and photographing powder horns, my book on Pennsylvania Screw-Tip powder horns Pennsylvania "Horns of the Trade" Screw-tip Powder Horns and their Architecture is now only available from Crazy Crow Trading Post
on line at : http://www.crazycrow.com/crafts/pennsylvania-horns-of-the-trade-book-preview.php
This high quality, coffee table style book is a great resource for identifying original Pennsylvania screw-tip horns, AND will provide the best information available for horn makers and students of powder horns to understand the original horns. There are over 440 color photos, with close-ups of both ends of each featured horn, along with general dimensions for the tips and butts of these significant powder horns.
A. J. DeCamp Custom Powder Horns