I hit a yard sale this weekend and spotted a small plastic box with hex keys and ignition wrenches for a buck. I have a terrible weakness for ignition wrenches, so I bought it.
When I spilled out the contents of the box I noticed that what I thought were hex keys were in fact Bristol Spline Drivers. I probably would have thought they were Torx, had the previous owner not labeled the masking tape that held them together in a set.
As you can see, they have 6 splines for positively engaging the Bristol screw head. There was one 4-flute driver as well. Of course I have only one object with Bristol spline screws — the rear sight on one of my vintage Sheridan air rifles uses a 4-flute screw. Unfortunately the wrench I have now is not the right size, which is typical. But at least I have them now in case I run across any other Bristol screws in the future! I do appreciate the previous owner taking the time to keep his oddball tools labeled.