Four Chinese characters - Qian Long Tong Bao / Boo Yuwan. The Board of Works mint. 21mm, 2.34 grams. Hartill 22.248ff. SKU T689-51254

This is an interesting and scarce clipped cash, with the outer rim being almost completely removed. This was probably done in the later 1800's, when small inflationary cash were being cast so this coin's size and weight were adjusted to match those of the small inflationary coins. Small coins like this one are rare. 

Emperor Gao Zong (Qian Long) (25 September 1711 - 7 February 1799) was the fifth emperor of the Manchu-led Qing Dynasty, and the fourth Qing emperor to rule over China proper.