This Casca Longus seems to have been a very close associate to Brutus. He belongs to the gens Servilius. Brutus had been adopted in his youth by an uncle who was also a Servilius.
Brutus and Cassius were first granted amnesty by the Senate before accepting positions of proconsuls that temporarily separated them. Both issued coins.
On October 8 in Zurich, Numismatica Ars Classica sells an aureus of Brutus, estimated CHF 500K, lot 23 on the bidding platform Sixbid, also shown in the post shared by Coin World. A better centered example was sold for CHF 850K before fees by the same auction house on November 18, 2013.
One side shows the head of Brutus from profile. The emaciated face carved in high relief is probably the only remaining realistic portrayal of Brutus in that period. This side is inscribed BRUTUS IMP. The coin has certainly been issued in 710AUC after a campaign by Brutus in Thrace which earned him the title of imperator.
When he was assassinated, Caesar had just appointed himself as dictator, arousing the horror among the republicans. His likeness on an aureus was felt as a provocation. The portrait of Brutus on a later aureus does not mean a betrayal of the republic but rather a tradition of Greece where he still was the Roman proconsul.
The other side shows military symbols aside with the name of Casca Longus without an effigy. This does not mean that Brutus shared any supreme power with his accomplice but rather that Casca Longus was his moneyer, meaning the responsible for his coinage (and not the engraver). The name of Brutus himself had appeared as the moneyer on a Republican coin issued ten years earlier.
The Brutus aureus thus predates the silver denarius glorifying the Ides of March by the inscription EID MAR, an example of which was sold for $ 546K including premium by Heritage on 7 September 2011. This ultimate denarius of Caesar's traitor is politically ambiguous, with an idealized portrait.