M-3 9/32-Drive Tee Handle
For as long as I have been fooling with wrenches the common sizes for a square drive has been 1/4" (quarter inch), 3/8" (three eighths inch) and 1/2" (half inch). There are bigger sizes like 3/4" and 1" square drive for things like bulldozers and steamship engines, but you don't see those very often.
Jack recently came across a set of antique sockets for sale on Ebay that supposedly had a 9/32" square drive. I thought it was nuts. Some guy has misread the measurements on some really old, badly worn sockets and decided that they were 9/32" instead of 1/4". Not quite. Jack digs around and comes up with the Alloy Artifacts web site, which has a whole page about old Snap-On (a brand name) wrenches, including, of course, 9/32" square drive. Hmmph. I could wonder what caused them to drop the 9/32" and adopt 1/4" size, but I won't.