Who, Hans Jacob? He left Switzerland in 1749, down the Rhine to Cowes, England. got to Philly, had to work off the indenture for his passage. His first wife and son died on the ship coming over. He got remarried in 1750, ended up in the SW corner of Virginia, had 15 kids. He was a cabinet maker. At least 4 sons made rifles. Abraham made some flintlocks so damned pretty they hurt your eyes to look at.
I'll do some searches on W. Alexander.
See all the other names on those records? Sounds like your ancestors were able to do gunsmithing. They undoubtedly prized them highly.
Look and see if your guys end up on the same unit rosters as Manuel McConnell or Timothy Murphy ~ bet they do ~ and not just William Alexander but also somewhere under Lafayette, Burr, Jefferson ~ i suspect you've got some folks there a tad more special than you might have imagined ~ also be sure to check for John Murphy with Clark.