I have found one example of a similar katar. Apparently with a 23" blade.
But I am concerned by the patina on your piece. As the others have mentioned buying anything from China with a blade is a risky proposition. The nature of the rusting is extremely consistent with other faked pieces I've seen in a variety of styles coming out of China. On the other hand a quick search on ebay didn't turn up an analog so you might be in the clear.
However I am concerned by how closely your piece resembles the one I posted. While I'm not an expert by any stretch of the imagination on katars, I do try to keep up with Chinese fakes since I have an interest in authentic Chinese pieces, and to my eyes the two are just too similiar.