The J. R. Pember Cancel? Handstamp? Machine Stamp? What is it?

So the stamp above showed up in a Kelleher auction this week and sold for $325.  The riddle of the J. R. Pember device grows, since there is no practical known use for a county clerk needing tax stamps and none of these cancels, heretofore known to me only on the one cent battleship, have any other stray marks like a manuscript complete date that was required by law.  There is a reason a clerk might have a stamping device for documents serviced in his office, and the clerk might have used a device similar to the one used by the Elgin National Watch Co to cancel stamps on documents, that produced a similar, clean, metal-type appearance.  It is also possible that a clerk might be a stamp collector, and might cancel a stamp with that device.  What else makes sense here? Ideas?