Yes, 1" hex for the cap screw and 1-1/4" for the nut. You might want to edit your post #3 above.
I still think the "1" was stamped at a different time than the rest. Notice that without it, the rest seem better centered. And the font is different, with a much thinner line.
Perhaps it was decided that the opening size should be included after the main stamping was done, and no one wanted to make a new die to include it. Or it was done in the field.
edit what?
The hexagon symbol followed by a "C" was fairly standard for Hex Cap in that era as far as I have seen (Billings, Williams, and Bonney wrenches, at the least), but it would be interesting to know, academically, who used it first. The only other marking I have seen for Hex Cap Screw is "CAP". I will add that these types of markings (whether Hex Cap and U.S.S., Hex Cap and S.A.E., or U.S.S. and S.A.E.) are clearer when they appear on two different lines, which was far more typical. Out of the hundreds of wrenches I have from this era, I may have seen it on one line only a few times, and I'd have to dig for those. I don't know why Billings strung it all together like that on this head, especially when the wrench in this case is much larger than wrenches they've used two lines for.Based on that, the use of the Hexagon symbol is a clever way of indicating the Cap Screw part of the marking.
I got confused by Mr.X's post #3 and thought he was referring to the USS fastener size being 3/4". Lugs post cleared up that the reference was for a 1" cap screw and a 3/4" nut. Based on that, the use of the Hexagon symbol is a clever way of indicating the Cap Screw part of the marking.
I thought Lugz had cleared this up in post #11.At this point I am wishing that the wrench in question really was from a Cleveland Class WWII Cruiser, which was the main reason I clicked on this thread!
Declaratively, to minimize misunderstandings, and so that others can more easily point out disagreement if there even is any...
The A.F. diameter of the head on a 1" Hex Cap Screw is 1-1/4".
The A.F. diameter of the head of a 3/4" U.S.S. bolt is 1-1/4".
The A.F. diameter of the nut for a 3/4" U.S.S. bolt is 1-1/4".
The milled opening of the wrench is 1-1/4", fitting 1" Hex Caps and 3/4" U.S.S. nuts and bolts.
Thanks, Jock. In that case, I am not sure why there was any confusion or disagreement. That is what MR. X indicated in post #3, and, after several exchanges that seemed as if you guys were in disagreement, that's what I re-iterated in post #11 and the now-deleted post preserved by MR. X in post #15.I used the chart on page 94 of the Plomb 18A catalog to find the USS sizes. It shows the 1-1/4" opening for 3/4" USS nuts and bolts and also for 1" USS cap screws.