An on-line ad for an old Goodwill store ads (dated 5/3/2010) mentions "Approx 11x8 Eric G Clarke and Co" for this game.
There was a small text ad in the Saturday Review of Literature, Volume 33 (1950), page 42 which reads"
DICTIONARY PLEASE! The game being played everywhere. Something not to be missed by
all who enjoy topflight acrostics, anagrams, and crosswords. For descriptive literature,
send postcard to: Eric G Clarke & Co., PO Box 1931, Portland, Ore.
The same ad ran in the Saturday Review of Literature, Volume 39 (1956), page 42.
EG Clarke's copyright of the name is noted in the Catalog of Copyright Entries. Third Series: 1954: July-December, page 1605, but the rules sheet for the game notes a 1951 copyright date.