Ron Guth: The Bar "Cents" first appeared in the American Colonies in 1785, when they joined the mix of motley coppers then in circulation. Their weight was too low to be valued at a Cent, but the name has stuck through use and tradition (in fact, the weight is almost identical to the U.S. Half Cents of 1795 and later years). The obverse copies the U.S.A. monogram seen on pewter buttons worn on the uniforms of Continental soldiers. The reverse consists of thirteen parallel bars, signifying the original 13 Colonies. Their simple, patriotic design makes them a favorite with collectors, although they are rather scarce and expensive.
Bar "Cents" were made in England, possibly at Wyon's mint in Birmingham (more famous for their Nova Constellatio Coppers). Various forgeries exist, ranging in quality from crude casts to excellent struck copies and electrotypes. All genuine examples have a small, thorn-like projection on the far right side of the bottom edge of the second bar from the top (this defect is seen clearly on the illustration above). Electrotypes will also show this projection, so authentication is mandatory.
Breen lists two specimens that are known on larger, oval planchets and speculates that they might have been "...some kind of special presentation or souvenir striking", but this is unlikely. Until the weights of these two unusual examples is ascertained, we can only speculate that they are normal strikes on misshapen blanks.