it is definitely not hong kong, the forst actual hong kong coin was a 1 mil coin of the early 1860's, this looks more like a 10 cash coin from one of the chinese provinces.
....thanks i went to a web site on chinese 10 cash coins all the coins are the same except for this marking which is in the center of the coin
It's from Hunan province. I call it the single character mark. http://www.gxseries.com/numis/china/china_province.htm There's 19 different marks for it - rather tough to collect all of them.
Not too sure to be honest but I am happy to fork out 10 dollars easily for yours. Definitely no longer one of those 'junk box' coin.