Sorting through a random selection of coins, mostly consisting of recent pre-Euro European ones, suddenly found this.
It is well worn off, the material seems to be a yellowish brass/bronze of some kind. Diameter is 24 mm, edge is smooth, thickness about 1 mm, weight 4.00+/-0.01 g (which is a bit weird, but may be just a coincidence given the wear). Medal alignment.
It seems to me that the characters on the obverse are:
乾
寶 通
隆
(Qianlong Tong bao or Ch'ien-lung T'ung-pao)
just like on these two coins:
https://en.numista.com/catalogue/pieces19927.html
https://en.numista.com/catalogue/pieces45597.html
which attributes the coin to the reign of Qianlong, the 6th emperor of the Qing dynasty (Manchu), 1736-1795.
And the Manchu characters on the reverse are very similar to these two coins too (Boo-ji and Boo-jyi). The size and weight also seem close, but not exactly so. The clearly visible middle loop in the right Manchu character makes it "jyi" rather than "ji", I guess? But the thickness of only 1 mm and the larger diameter is too far from the Qianlong Boo-jyi as it is described in the Numista catalog (d = 21 mm, h = 2 mm, w = 4.16 g)
So, my first question is, how likely is it for this coin to be genuine? I mean, it probably makes no sense to fake such a low-value coin, but who knows what the Chinese tourist industry is capable of? 18th century and all... The weight of exactly 4 g might indicate modern standards of industrial fabrication...
And, second, if it is genuine, can you please help me to figure out what it is? Thank you!