Had to check how many of my guns have Weavers..... That was easy because each gun has its own folder of several pictures right here on the computer. Turns out there's seven with Weavers and all but one have that screw oriented to the left....... All scopes were mounted by yours truly. I think they just looked better visually at the time. The one gun with those screws oriented to the right is a Mossberg 500A camo 12 ga. turkey gun. Bought it used and unscoped in 1999 and put on a 2.5x 20mm Leupold two years later. And now I can't recall why it's the only one that has the screws facing to the right. Doesn't affect the functionality of it in any way and I still don't know why it got mounted like that..... At this point as long as it works I don't care. Nowadays I lean toward those vertically split Warne rings or Leupold PRW's.
