Rock Island Auction Company had another original Hawken rifle at the CGCA show in Denver this past May (see
http://americanlongrifles.org/forum/index.php?topic=56131.0 for an S. Hawken rifle also at the show). This one is an original J&S Hawken. It was originally a full stock but had been converted to half stock sometime in its working life. It's stocked in walnut.
The lock is marked "ADOLPHUS MEIER & Co." According to Hanson in
The Hawken Rifle: Its Place in History, "Adolphus Meier...first set foot in St. Louis March 2, 1837 (Edwards and Hopewell, 123)." He started advertising in local papers in 1838. This probably establishes the earliest possible date for this rifle, but Meier maintained his business into the 1860s, so the lock doesn't provide a very narrow bracket of for the date.
The rifle has typical J&S period features such as the round scroll at the back of the trigger guard and the "comma" shaped snail on the breech bolster. The breech is not hooked but a fixed patent breech typical for J&S full stock rifles and a few half stock rifles. The snail is similar to the one on the John Brown full stock J&S Hawken in Salt Lake City.
John Brown J&S Hawken BreechThe John Brown Hawken also has an Adolphus Meier lock. According to the research cited in the literature, Brown purchased his rifle “in St. Louis on March 24, 1845. He bought the rifle as he and several other young men were en route from Mississippi to Nauvoo, Illinois to join the Nauvoo Legion.” The John Brown rifle and the subject rifle could be contemporaneous.
John Baird showed a picture of the subject rifle as Plate 40 (bottom image below) in his second book, but it's not clear that he had personally examined it because the caption under the photo seems to express some question as to whether it was originally a full stock.
Viewing the rifle at the CGCA show, I don't think there is any question it was originally a full stock. It has a square cheekpiece that is, as far as I know, exclusively seen on J&S full stock rifles.
The nose cap is pewter and not the typical Hawken shape due to the lack of an entry pipe. The barrel is described as 39 1/2 inches long, which may be its original length. The description says it's .54 caliber. The single barrel key also suggests a full stock cut back to half stock.
The barrel is stamped with "J & S HAWKEN ST. LOUIS" on the top flat behind the rear sight.
The rifle sold for $74,750 including buyer's premium at the Rock Island Sept 8, 2019 auction. Here's a link to the listing.
https://www.rockislandauction.com/detail/77/3054/documented-js-hawken-halfstock-percussion-rifle