Here are the advertisements that Dan refers to:
October 1978 ad from Buckskin Report
February 1979 ad from Buckskin Report
April 1979 ad from Buckskin Report
These ads clearly indicate that Allen was trying to develop the Santa Fe Hawken and the Baird-Webber J&S Hawken rifles at the same time.
Unfortunately, Allen ran into trouble with Olin about the same time and probably had other difficulties as well. The net result was that his company was reorganized into two separate companies as indicated by the following ads from the July 1980 issue of Buckskin Report.
I had previously stated that Allen Firearms went out of business in 1987. My source for this information was the Blue Book of Modern Black Powker Values. I now question if this is correct because I cannot find any reference to Allen Firearms after 1980. If Allen Firearms did cease to exist after 1980, this might explain why the Baird-Webber J&S Hawken rifle never came to fruition.
Uberti continued to produce the Santa Fe Hawken after the demise of Allen Firearms, and it was sold through Old-West Gun Co., now Cimarron F.A., Track of the Wolf, the Log Cabin Shop, and probably other outlets well into the 1990's.
Hammer, I have been unable to find any reference to a Uberti, or any other Italian made, Hawken prior to the dates that I mention earlier. That's not to say that they don't exist, but I couldn't find any advertisements or any mention in the muzzleloader magazines of the period. The features you mention, the slant breech and that tiny half-dovetail that locks the toe plate edge to the toe of the butt plate, are present on Uberti's Santa Fe Hawkens made after 1979.
I did see a Uberti Hawken kit offered for sale on Gunbroker.com earlier this year that had a beautifully figured maple stock and color-cased furniture. Evidently, they did make their Hawken with stocks other than walnut.