First of all I'd like to say hello, and it looks like a pretty nice site you guys have. A friend of mine gave me a project to find out what kind of coin he has, and I thought you guys would be able to help me. Below is a photograph.
Info from Hartill's: Cast Chinese Coins : Qian Long Tong bao 1 cash, cast brass. 1768-73. H22.213 Board of Revenue Beijing mint, West Branch *This was given to me by another member(ls8driver) a few monthes back. Oh, nearly forgot. Welcome to the forum!
From what I could find though, it doesn't look as old as http://primaltrek.com/coinlegend.html said it is. The one they show there is very similar to the one I have, but slightly different.
In the left picture the top is at the 4:30 position, and in the right picture the top is at the 7:30 position.
Very close, but this one is slightly different. Emperor Gao Zong, Qian Long reign, 1761-1767, Board of Revenue mint, West branch, Hartill 22.206
Not the year, but the time period of anywhere from a few years span, to several decades, depending on the ruler and mint.