Kharns,
I'm not an expert on Swivel knives, maybe someone else will pile on, however, I have used and sharpened them for over 45 years so here's my $.02, only one face and the traditional wisdom is that it should be 30 degrees. There are jigs for sharpening swivel knife blades ( a really good one is the Big Red), they are adjustable as to angle however, the Big Red comes with a jig for setting the angle and it is set to 30 degrees. The blade should be very sharp, it should easily "slice" the leather, it should not gouge the leather.
Hope that helps,
Chief