100 Rupees Civil Aviation India

Issued to mark the centenary of civil aviation in India, this coin commemorates the 1911 Allahabad-Naini airmail flight — the world's first official airmail service, which predated the better-known British and American airmail programs by several years. Henri Pequet flew approximately 6,500 letters across the Yamuna River on February 18th of that year, covering roughly 13 kilometers in a Humber biplane during the United Provinces Exhibition.

The .500 fineness is characteristic of Indian commemorative coinage of this period, a deliberate policy choice that kept silver content costs manageable across a large commemorative program without dropping to base metal entirely.