Hong Kong cent 1923 - Overstrike

I recently got this coin in a lot. It is a Hong Kong cent, dated 1923 and appears to be struck over a Chinese 10 cash coin. I am wondering if anyone here knows how common (or rare) this is.

 I really dont know what to say. The flag pole looks raised in the field. So i dont think it a vise job.

The 10 cash has a larger diameter than the cent a real puzzler this one 

A little googling and I found another example of a 1923 Hong Kong cent struck on an earlier (c. 1905) 10 cash coin. Since the HK cents were produced at the London mint, I doubt they used old Chinese coins, and the strike quality also does not appear up to Royal Mint standards of the time. I suspect this is a contemporary counterfeit.