The one in the photo looks like a type 3 with the lock facing out and a flip up handle. Type 2 have the lock facing in and the handle lifts up and down.
To get them off, unlock the clamp at the lower front of the case and open it. Slide the case back a couple inches and lift up and out. A bit of wiggling is usually necessary on my bikes to get the case out from under the turn signal.
Patience is important, it took me over a year before I figured out the trick to getting them on and off the bike without taking 5 minutes. As hard as they are to remove, they seem to have no problem coming of when you are heading down the road, especially the scarce City Cases, of which I have lost two so far.