Zee, I used to use this style vise on a surface grinder for "precision" grinding.
The vise is precision ground ground square & perpendicular, & can be used on it's
side. The screw & pin/ball create a wedge type clamping force that force the workpiece down,,
unlike a screw type vise that has a tendency to twist & rotate the workpiece when clamped. (Vised?)
John