It still looks like the Indian (Assam) 1/32 rupee (KM 245) at less than probably 6mm is the smallest and it's 19th century. The 1/16 rupee (KM246 is 7mm and .67-72 grams is listed at 7mm. The 1/32 should be half that size and it's listed at .34-36 grams. Both are silver. The later 1/32 rupee (Km 260) from another ruler is listed at 6mm and .34-.36 g.