15 degree wrench jaw angle?

Probably in the dark mists of time. 15 degrees gives you 30 degrees when flipped over to avoid an obstruction, where straight jaws offer none.
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Google=92s patent search shows =93wrench=94 patents going back to 1783. Just skimming those or =93wrench + angle=94 doesn=92t show any clear answer. Peterson adjustable wrench patent in 1915 (US1133236) mentions the advantage of having the opening of his wrench at an angle to the handle to improve the sweep of turning the nut, but doesn=92t specify this angle specifically. He mentions both hex and square nuts in his patent. Maybe it=92s simply that 15 degrees is a common coefficient for both the 60 and 90 degree faces found on nuts. Interestingly, there=92s a patent for a ratchet wrench in 1796 (US546672).

Probably about the time that screw machines started turning out hex nuts instead of guys making square ones one at a time via anvil, vise and tap. I've got some old wrenches out of car tool kits from granddaddy's collection of Stuff, some are straight in-line with handle, some have the opening at 90 degrees. A couple have both, same size opening on both ends. I have some of the S sort, I think those were intended for proto-obstruction-type use, like bolt heads in a circle. Or maybe getting starters out. Box-end wrenches seem to have come into use somewhere in the '30s, I've seen some ads for "Box- socket" wrenches in some really old PSMs. The oldest open-ends I have that have 15 degree ends are Williams brand. Odd 32d sizes, too. For Whitworth heads maybe?
Stan