I have this thing that, when I look at something, it might just hit me a certain way. And it then sticks in my memory.
I was just surfing thru AA one day, and came upon these OE's with the funny hollowed out shape near the end. That image just stuck. And the letters NDF.
When I saw your wrench, that little memory fired. And I found it in about 2 minutes on AA. Was kinda pleased with myself the rest of the day knowing I solved a little tool "mystery" before anyone else did. lol