So what is "DVS?" (Say the letters a few times and you'll get the word play.) It's a system for marking freely selected cards so you can later find them by feel. And the DVS substance also serves a secondary purpose that can come in handy with specific card tricks.
I'm not certain that I would want to mess with "DVS" in my strolling sets. But it's great for fooling other magicians as the method is out of the ordinary.
You can read my review here.