Bengal Sultanate (1203-1576) 1433-1459 Unlisted and first known silver tanka of Nasir al-din Mahmud , mintless type, Bengal Sultanate, India - known before only in gol

Nasir al-dunya wa'l din abu'l muzaffar Mahmud Shah al-sultan / Nasir al-assalam wa al-muslimin khalladah malkeh. Na date and no mint. Small silver coin but at proper tanka weight - 23mm in diameter, 10.59 grams. "The coins of the Indian Sultanates" B-450 (for a gold tanka).

This crude type is known for a gold tanka and a silver half-tanka, and was never published for a silver tanka coin. This is the first known coin of this type known.