The tetradrachm planchets are generally thick, with well defined edges, giving the coins a substantial presence. They look fairly impressive when compared to some of the low relief contemporary coins of other regions. That is, the planchets were cast in an open mold with tapered sides. This facilitated the easy removal of the cooled blank. Due to the vastness of the series, collectors often concentrate on one or the other of these two categories.
References also tend to be divided somewhat into the two categories.
Catalogue of Alexandrian Coins. Monete Imperiali Greche - Numi Augg. Curtis covers only the tetradrachms, and the other references cover a broader range. However, all four of the above are the catalogues of specific collections. In other words, if the collection did not possess a certain scarce type it is not included in the catalogue.