In terms of pattern coinage, Kneass, who was appointed to the chief engravership at the Mint on January 29, 1824, was a nonentity, an also-ran. In fact, we are of the opinion that there is not a single United States pattern coin design that can be attributed to Kneass.
There is a fiction (in the opinion of the present writer) that William Kneass designed certain pattern half dollars of 1838, but this is probably based upon a biography in the American Journal of Numismatics, July 1883, by Patterson DuBois, a Mint employee, who probably was not aware that Kneass had suffered an incapacitating stroke on August 27, 1835, after which Christian Gobrecht did virtually all new work on patterns, dies, etc. The DuBois commentary is given herewith, excerpted, as it also relates life dates, etc.:
"WILLIAM KNEASS, second of the line, was born in Lancaster, Pennsylvania, September 1781, and was appointed engraver, January 29, 1824. Mr. Kneass had been chiefly a plate engraver for bookwork. There were some changes in the coinage during his term, notably in 1834 and [QDB note: here comes the authority for later work] 1838 for gold, and 1836, 1837, 1838, and 1840 for silver. But some [italics added; should be all] of this work was done by Gobrecht as assistant. Kneass appears upon a pattern half dollar of 1838; but the silver dollar of 1836 as well as a pattern half of 1838 were the work of his assistant. Mr. Kneass is well remembered as an affable, genial 'gentleman of the old-school, who had the rare quality of engaging and winning the esteem and affection of children and youth, in whose companionship he found rich delight. Prior to his appointment he had an engraving office on Fourth above Chestnut Street, Philadelphia, which was a well-known rendezvous for the leading wits and men of culture, for which Philadelphia was then eminent. Mr. Kneass died in office, August 27, 1840. A good engraving of him hangs in the Assayer's Office, inscribed 'to his friend Adam Eckfeldt, Chief Coiner,' who had been chiefly instrumental in securing his appointment.…"
In The Numismatist, July 1940, well-known collector and student F.C.C. Boyd perpetuated the fiction of Kneass and the 1838 half dollars, probably inadvertently, as Kneass most certainly did not sign any half dollars of this date (or of any other date): "Preserved in the Assayer's Office of the U.S. Mint in Philadelphia is an engraved portrait of Mr. Kneass as engraver and diesinker at the U.S. Mint in Philadelphia, on January 29, 1824, succeeding Robert Scot. Kneass was born in Lancaster, Pennsylvania, September, 1781, and his first training as an engraver is unknown, but he became famous in Philadelphia in 1815 and remained working at his profession there from then till his death on August 27, 1840. Most of his work is in line, but he gained considerable attention for some good aquatint views. Two different firms bore his name, Kneass & Dellaker (Delleker) and Young & Kneass & Co., general engravers. He served in the War of 1812 as Volunteer Associate of the Field Engineers, who constructed fortifications on the western front of Philadelphia. In commemoration of this he engraved, in 1815, a plan of this work after the drawing of Strickland, a famous artist of the day and one of Kneass' best friends, for whom he named one of his sons. Of his six children two became famous. Samuel Honeyman Kneass, as architect and engineer, and Strickland Kneass as an engineer. He is credited with engraving many of the dies of the gold coinage in 1834 and 1838, the silver coinage in 1836, 1837, and 1838. Also, his name appears on a pattern half dollar of 1838, but the silver dollar of 1836 and another pattern half dollar of 1838 were the work of his then assistant at the Mint, Christian Gobrecht, who succeeded him as chief engraver on December 21, 1840."
The obverse on the following design has been traditionally represented as being the work of Kneass - J73/P77 - although this is now brought into question per the above biography.
Image of William Kneass courtesy of Heritage.