Arthur was issued as part of Alphabet Innovations, vol. 1 [Martin] from March 1969, or in vol. 2 [1976 specimen] from Sep. 1969. It was designed by Roc Mitchell [Mitchell].

See also Bentley, a “revision of ‘Arthur Thinline’” [Taylor] drawn by Joe Taylor for Lettergraphics. Lettergraphics also had the original Arthur as “425-1 (ref. Arthur)”. Castcraft carried it as Light Knight [Castcraft 1978] and Lettering Inc. as Photo-Artline. [Switkin 1976]

King Arthur is a variant with stroke contrast.

Mitchell showed a digital version of the Arthur series as Poetry. [2000 web archive] The new name was introduced in 1993. [Oka]