Aprippa is an Italian name, from about the time of the Ceasars. It may also be the company that made the clamp for Williams. BTW, while that is a very large and strong clamp, it is not as beefy as the one the OP has.
Agrippa was a registered trademark of JH Williams, like SuperWrench, SuperAdjustable, Vulcan, etc.
Since Williams was one of the major players as far as drop forging was concerned, I can't imagine them contracting someone else to make one of their signature items.
The Agrippa was their line of medium duty clamps. Their heavier duty line of clamps were branded as Vulcan. The Vulcan clamps were much thicker across the body and originally didn't have the grasping and lightening grooves running down the body like the Agrippa clamps.
In later years, the Vulcan trademark was used with their less expensive hand tool line and can be found on light and medium duty clamps of late vintage.
You'll know one of the original Vulcan clamps when you see one.
Live long and prosper.... (couldn't resist)
WoD
Each!