Victorinox 84mm Watch Opener - Renata Batteries. Edit 2018-01-29; Some have asked about the functionality of the small watch case opener blade on this knife and other similar blades.. There are a few different designs made and used by Victorinox and Wenger. This one is probably the largest in actual size. The edge is not sharp like a real blade but is fine enough to fit under the edge of a watch back to lift it up for battery replacement. The alox versions of this knife have a smaller version of the watch case opener blade and I feel it offers a finer edge and maybe easier to use, but that is just my opinion. Click the tag "Watch Case knife" at the bottom here to see other examples of these knives and tools.