Hello, leg17. Well, at least I got 1 thing right today!!!! Could you please explain the meaning of that symbol in relation to the other wrench markings? Thanks, Lou
Standards for Opening Sizes
The wrench model number specified a combination of opening sizes, but the means of describing the sizes added further confusion. In the late 19th and early 20th centuries, wrench sizes were commonly named by the nominal size of the bolts whose nuts they fit, rather than the size (across the flats) of the nuts themselves. For example, a "1/2" opening might fit a 7/8 (across the flats) nut threaded on a 1/2 inch bolt.
To further compound the confusion, there were at least three different standard systems for nuts and bolts:
The U.S.S. or U.S. Standard,
The S.A.E. or Society of Automotive Engineers standard, and
The Hex Cap screw standard used by hardware manufacturers.
The latter convention was often indicated by a hexagon symbol followed by "C" or "CAP".These multiple standards meant that some wrench openings might be marked with three size indications. For example, a number 23 wrench would be marked "3/16 U.S.S." for the small opening, and "1/4 U.S.S.", "5/16 Hex Cap", and "5/16 S.A.E." on the larger end. Also, the U.S.S. size was sometimes marked as "NUT".
This confusing system of multiple size standards persisted until around 1927, when it was phased out in favor of the across-flats size.
http://alloy-artifacts.org/table_oe_wrench.html
