Mine works, but is not "original". It is basically a rectangular block with two holes in it. The first hole goes through the middle and is threaded for the lock bolt from the top of the clamp. The second hole sits on the chin and locks against the bottom of the lathe bed (I'm calling this the "front"). Both holes are threaded.
View attachment 312681
View attachment 312682
It's 1.75" wide x 1.9" long x 0.6" deep. The hold-down hole (that the bolt through the clamp runs through) is centered side-to-side, but is 0.9" away from the back. The adjustment screw hole along the front side is 0.3" from the front of the block. Put a bolt through it (or a threaded road and a nut to lock it in place, and you're ready to install and lock it down.