I pulled out Dr. Bailey's British Ordnance Small Arms, 1718 to 1783. It seems the hole in the top jaw screw started showing regularly on miitay pistols of about 1750 onward and on musket locks from some use in the pattern 1756 and 1763 muskets and then became rather standard on the pattern 1777 onward, including some of the British Military Rifles from that pieriod onward. So I stand corrected on British Military guns.
This queston picqued my curiousity, so I had to do a little more digging. Since I used to collect early gun tools, I remembered the "Y" shaped Brown Bess musket combination tools and that they went back to the 18th century. The end of the Y shaped musket tool was formed like a tapered round punch. Some people erroneously have stated that was to clear the touch hole, but those punches were too big for that. Then some suggested it was for driving the barrel pins out to clean the barrel. I never bought that because you don't want troops dismounting barrels and losing the pins. However, they worked nicely to tighten top jaw screws with holes in them. Now as more research has been done, we find most of the dug examples they made copies from were so rusted that the threads on the rounded tapered punch leg were worn away and after checking originals, they found most of them had threads for a worm. Most reproductions are not made that way. Here's a link that shows a dug original.
http://paaba.net/Projects/ZMusket.htmI'm very glad to have researched this more as I found out something I didn't know about the 18th centuy Y shaped musket tools. I already reshaped and rehardened/annealed the two screwdriver tips on my repro tool to correctly fit my Brown Bess. Now I'll go back and thread the tapered punch end so I can use the outer edge to tighten down top jaw screws and hold the worm in place further down towards the center. It will make the tool even more useful.
Gus