Below is a review of Sopwith published in 1989 as part of an article by Bob Liddil in “Portable 100 Magazine” (the full article can be found here).
Bob mentions that Sopwith is available for $12 as part of The SSB Portable Pastime Package, which he had reviewed the previous year in Pico Magazine. But wait! A quick search reveals that the same Bob Liddil was also the founder of The Programmer’s Guild which published the package! An interesting coincidence.