While perusing some online manuscripts at the Staatsbibliothek Berlin, I came across some pages from the Musikalisches Kunstbuch by Johann Theile (1646-1724), and saw something very much like Endler's canon from the December 2015 puzzler staring me in the face. I would be remiss not to draw attention to the connection.
It seems quite evident that Endler's canon is based on Theile's, but is less robust. Theile gave one voice, yielding three (and four in another solution), but Endler continued the middle voice in free counterpoint against the missing, further-augmented voice.
None of the other four canons in the set of five seems based on canons by Theile's Musikalisches Kunstbuch, only number 3, the one I selected for the puzzler (December, 2015).
Comparing the two solutions, one can see that Theile's is more complex, both in its counterpoint and in its canonic relationships. But to be fair, Endler has contributed his own counterpoint and introduces the second voice a compound sixth below the highest voice rather than a double octave. Theile also gives a four-voice solution to this canon.