James T. Deacy invented the first double-writing implement, a gimmicked pencil, for his “Just an Echo” in The Jinx, No. 29, Feb. 1937, p. 185.

Ed Mellon developed the idea further with Instrumental, a cleverly gaffed ballpoint pen, which he marketed in mid-1953; see J. G. Thompson, Jr.'s review in The Linking Ring, Vol. 33 No. 6, Aug. 1953, p. 84.

See also Confabulation.