Of interest is that the classic Doyle bibliography does not give all of the Doyle Altemus books. Green and Gibson in A Bibliography of A. Conan Doyle (1999) lists Beyond the City and The Sign of the Four. No dates or other information is noted.
For completeness, Henry Altemus in its Printemps Series of 1895 (see http://henryaltemus.com/series/series152.htm) also published A Study in Scarlet and A Case of Identity. All the books in this series had the same cover illustration drawn by Archie Gunn.