I have wanted one of these for a very, very long time, but have never been able to score one at anything resembling a decent price. These are the first unambiguously Kushan coins, the last and only Kushan silver coins, and probably the last native Indian silver coins made until Nahapana.
Kushan tribe (not yet empire)
"Tyrant" Heraios, early 1st century? (Probably posthumous)
AR Obol (10mm, about .60g)
Diademed head right
Heraios standing, gesturing to right, degenerate legend the originally read "HPAOY KOPPANO" for "Heraiou Koshshano"
Rare

The Kushans were originally a tribal confederacy in what today is Mongolia. The Chinese referred to them as Yueh-Chih. They were driven from their homeland in the mid to late 1st century BC (in the wake of the Han-Xiongnu wars) and settled in Bactria, probably dealing the death blow to the remnants of the Indo-Greek kingdom. The Kushans seemed to have usurped power from the Scythians following the death of Azes. They issued a series of silver coins loosely based on Greek prototypes, but "Heraios" was the first to use "Kushan" on his coins.
The tribes were unified into the Kushan Empire by Kujula Kadphises in the first century (some of his coins copy those of Augustus) and were propelled to greatness under Vima Kadphises, around the time of Trajan. For unknown reasons, the Kushans stopped using silver rather abruptly, using thick bronze coins for daily transactions and gold staters for international trade.
Heraios is not mentioned in the Kushan kings list, and it has been argued that he may have been the same person as Kujula. He issued only tetradrachms (which cost the better part of a thousand bucks) and obols - no denominations in between.