So yesterday afternoon I internetted the heck out of these tools, trying to learn what I could about them. Turns out there are at least FIVE distinct variations, maybe more. Most of the differences are pretty subtle, but here's what I found. Variations 1 thru 5 match up to the pictures below, in the same order.
Version 1) Stamped with 1896 patent date, and have a protruding "bossed" pivot. These tools have notably longer jaws than later versions, and the wire cutter notch is located between the jaws. Produced in 6, 9, 12 inch sizes, and possibly others.
Version 2) Stamped with 1896 patent, and have a flush pivot. Jaw length has been shortened to “normal” length. Wire cutter notch has moved to the side of the pivot. Old ads claim it was available in 6, 7, 8, and 12 inch sizes. (Photo from Alloy Artifacts)
Version 3) Stamped with 1903 patent date. Still has flush pivot, outboard wire cutter notch, etc. 1903 ad claims it was available in 6, 7, 8, and 12 inch sizes. (Photo from Alloy Artifacts)
Version 4) An "Improved" model was introduced ca1905 according to publications of the day. A hardened steel lower jaw insert was added for better gripping. Center pivot is still flush, with outboard wire cutter notch, etc. 1905 ad claims it was available in 6, 7, 9, and 12 inch sizes. (Photo from Alloy Artifacts)
Version 5) The "Improved" model was improved even more, with the change to a screw-and-nut pivot. This allowed the pivot to be tightened after it had loosened up with use. (The flush-pivot versions I have handled have been rattly-loose at the joint, so I assume it was a common complaint back in the day.) Unknown what sizes these were produced in.