"Uncle Dan Lefever - Master Gunmaker" is the expanded version of the above cited book; Robert Elliott is the sole listed author on the Uncle Dan book.

The 1958 article contains some misinformation. Here is a link to photos of most of the grades of the D M Lefever "cross bolt" guns - they start about 3/4 of the way through the photo section.

http://www.lefevercollectors.com/index.php?p=1_18_Photos