Two Chinese characters Ban Liang ("Half an ounce"), inner rim ONLY above and below the hole, complete outer rim / Flat, no rims. 25mm, 2.57 grams. Gratzer/Fishman "The Early Round Coins of China" #13.158; Hartill #-. SKU T1905-50089

Late issue, rare with the inner rim ONLY above and below the hole and a complete outer rim, not listed in Hartill. "Shanzi" liang describes the shape of the character "liang". It is a distinct calligraphic variety of character "liang", used mostly in the Han period. 

A Chinese ounce (liang) weighs about 16 grams. The earliest "Ban Liangs" weighed half that much - 8 grams, but the later pieces, like this one, weighed much less. These late Ban Liangs were cast during the reign of Emperor Wudi (140-87 BC), the date of the casting is ca.136-118 BC and they come from the last issue of Western Han dynasty Ban Liangs.

This coin is unconditionally guaranteed to be authentic