Double Angle Sine Plate

Description

6.375 inches by 12.000 inches.
The table has equally spaced 1/4-20 threaded holes for workholding, and two movable side plates to locate the edges of your piece.
This is a solid, heavy tool: it weighs approximately 70lbs.
It has no visible signs of ever having been dropped or mishandled.  Its condition is like new.
The only identifying marks on it read, "NCR ACD," which I believe are related to trigonometric formulae, and it has a serial number.
I've searched but I haven't been able to find another sine plate just like this one.