From Google: Cross sliding vises are used to hold workpieces in place while drilling, milling or tapping in two axes. Cross slikding vises have hardened v - grooved jaws for clamping objects vertically and horizontally. One of the photos details the characteristics of the vise. 

Please feel free to contact me with any questions. Take a moment to peruse my collection of curiosities. There are many rare and unique items that would make great gifts for your friends and family (and who knows what else you may find for yourself)!

Thanks, Johnny