Ottoman Empire, Mustafa III. Large Silver Piastre Coin. Denominations: Piastre References: KM-321.2. Mint Year: 1767 AD (AH 1181) Mint Place: Islambol (Constantinople) Diameter: 36.8mm Weight: 18.27gm Material: Silver Obverse: Mint formula and accession date (1171), date of issue (1180) above. All within pelleted border. Reverse: State seal (Tughra) of Sultan Mustafa III within pelleted borde ...