I have a HW5. It is an eight shot .22 lr revolver, with a swing out cylinder. I bought it at a gun show for $100. It was made in Germany, and the company, as I understand, is no longer in business.
Mine is chrome plated, very tight, and even shoots about where it is aimed. I carry it on my trapline for dispatch of the more agrerssive animals, and it gets a lot of abuse and exposure to the elements.
As for the HW9, specifically, I have no information.