Thanks for posting these pictures!
I can’t really add anything with regard to makers, but I understand that some Hawkens were un-marked. The Lacome rifle in the New Mexico State museum, is also generally believed to be a Hawken, although it is not marked as such. In his book, Sporting Firearms, which has a chapter on Hawken rifles, Mr. Kephart wrote that he bought his Hawken from William Albright, a gunmaker and dealer in St. Louis, in 1894. Regarding his Hawken rifle, Kephart wrote, "It lacked the maker's name on the barrel, but Albright said the Hawkens would not put their 'brand' on a gun that they made for a firm that made guns themselves....
Regarding the Kephart Hawken in the glass case, the placard states it is .58 caliber, and dates to 1845. The rifle Kephart described in his book was .53-.54 caliber, shooting a 217 grain (half ounce, or 32 gauge) ball. Also, I believe the rifle he used in his famous test was of very late production, from well into the 1850s. As noted above, Kephart bought his rifle as "new old stock" in 1894, and showed it to Charles Siever, a former Hawken shop workman. The old gunsmith reported that he had made the lock, "...more as forty year ago," which would put the date of manufacture in the 1850s.
Kephart wrote that he donated his Hawken to the Missouri Historical Society in 1901. While he mentioned another Hawken that was donated by another individual, that rifle also took a half-ounce ball. Kephart only described donating one Hawken, himself. So, I think it is likely that Mr. Kephart either owned more than one Hawken rifle, with a second one being donated after his book was published, or the information on the placard is not entirely correct. Museum curators, bless their hearts, are rarely “gun guys,” and labeling errors occur frequently.
Again, thanks for sharing the images and starting the discussion!
Notchy Bob