"Jake" Clinkenbeard's first name has not been verified, but may be John C. Clinkenbeard, son of William clinkenbeard, of PA and later Bourbon County, Kentucky. If so, he was born in 1755 in Cumberland County, PA. He served in the Rev War, and his family moved to Kentucky sometime after the war. John was in Fleming County, KY and later Bourbon County with the rest of his family. He shows up in the 1820 and 1830 censuses, and died in nearby Clark Co. in 1837.
Jake Clinkenbeard made rifles in the Lexington (KY) style. Two of his rifles, one pre-War of 1812, and one post-War of 1812, are illustrated in "Kentucky Gunmakers 1775-1900." Both have typical Lexington style patchboxes. Neither rifle is signed, but both have strong provenances from early family members of the original owners, stating the guns were made by Jake Clinkenbeard. His rifles were rather middle-of-the-road for Lexington guns, not fancy, but nicely stocked with Lexington style patchboxes. No other inlay work is present on known guns.
I have never seen a signed Clinkenbeard rifle. If by chance your museum has a signed gun, I would greatly appreciate seeing pictures of it, to compare with his other known guns. If by chance your museum would want to purchase a copy of "Kentucky Gunmakers 1775-1900" for further study of Clinkenbeard, ordering information can be found on this web site under the "Recent Books" forum...
http://americanlongrifles.org/forum/index.php?topic=27273.0 Hope this helps you. Shelby Gallien