Possible Prototype struck in gold, the FINEST of 3 certified by NGC. Experts think that this example may have been over struck another worn Double Daric. 
This is an overlooked rarity next to the popular Alexander Distater and Persian Hero-King Double Daric. 
Essentially a gold version of Mazaeus’ famous silver staters of Tarsus in Cilicia, this piece shares their type but lacks any legend. It is likely an early emission struck by Mazaeus as he changed allegiance from the Persians to Alexander and appears to be an overstrike over another coin, possibly a double daric with the Hero King obverse that circulated under the Achaemenid Persian Empire (the thick lines discernible in reverse field are suggestive of the reverse types characteristic of these coins). This piece is an exceedingly rare variant with the lion and bull facing left, the best graded in a population of 3 encapsulated by NGC.
Mazaeus was the Satrap appointed by the Persian King Darius III to rule the region as Satrap or Governor  of Babylonia. After Alexander defeated King Darius III (the last Persian King). He gave Mazaeus a choice, continue to govern this area in my name or be replaced and die. 
Several interesting theories have been floated around that give meaning to the design of this coin. The obverse resembles what experts believe could be Zeus seated on his throne, a feature that is on all of Alexander the Great’s Silver Tetradrachm’s. On the Reverse we see the use of the famous “Lion and Bull”. Possibly paying respect to the ancient Empire of King Croesus of Lydia whom the Persian’s defeated and were given the secrets of the coin making process.