I picked this up a couple weeks ago at Martin Donnelly's July auction thinking that it was just a standard version of this wrench. It is patent no. D57,068 that was issued to a George Allen of South Bend, IN on Feb. 8 th of 1921.
It is in the DATAMP data base as a Kento wrench. I'm not sure that this is correct. If you look at the picture carefully you will see that a large K is in the lefthand arrowhead and a large O is in the right hand arrowhead. The portion that connects the two arrowheads has the letters ENT although not as large as the K and O. It seems to me that this could just as easily be KO ent for enterprises, a not uncommon way to express things.
I searched for Kento and only found the DATAMP reference. A similar search for KO ent. Found nothing. I found this wrench, called a Benton, on a web site but with a significant difference. The one I have has a knurled ring just below the handle that may be rotated clockwise so that the handle may not be rotated until the ring is rotated ccw. No lock ring is shown on the patent.
It also seems strange to me that no utility patent was filed. This wrench is unique enough in its operation that I would have thought that Mr. Allen would want to protect its workings.
It is not evident from the patent how it works so I'll try to explain it.
Turning the handle so that the rack lines up with the notch in the handle, allows the lower jaw with the rack attached, to move up and down. The lower jaw is manually moved up to contact the nut to be tightened and then the handle is rotated clockwise. This causes the lower jaw to move forward by the amount of the rack pitch, thus removing any clearance that might exist between the jaws and the nut to be tightened. Turning the lock ring at the bottom then prevents the main handle from turning. Reversing the procedure releases everything.
Overall length is 7 1/2 in. Max jaw opening is 2 in. And the jaws are 1 1/2 in. deep.
