Alexander III, The Great

This represents the general style of the large variety of issues from this famous Macedonian conqueror. Head of Hercules (Herakles) with lion skin; Rx: Zeus seated on throne holding eagle and sceptre, there's a crossed devise in the field and the Greek word for Alexander behind.
This example weighs ~2.9 gm at 19mm (hemidrachm?); but doesn't seem to fit the Thraco-Macedonian weight standard or the Attic standard either. Origin unknown, any help on an attribution and authentication would be appreciated. Please comment.
Articles to VIEW and DOWNLOAD:
An excellent article that features a story about the discovery of the only known living portrait coin that shows the image of lifetime portrait of Alexander the Great (not Herakles)is linked below. It's a MUST read!
Ptolemy's Egypt & Alexander's Portrait - Holt: Ptolemy's Egypt & Alexander's Portrait - Holt
Here's a very informative & illustrated paper on "The Spread of Coins in the Hellenistic World" by A. Meadows: Coins in the Hellenistic World A Meadows
Hellenistic Coin Portraiture - Sheedy: Hellenistic Coin Portraiture - Sheedy