Odd sized drive - Snap On sockets

[MJOPE]

A while back bought a bunch of various sized and brands of sockets at an estate sale and there were a few Snap On sockets that looked like 1/4” drive. I threw them in my tool box and today I was looking for a 5/16” deep socket and remembered I had those Snap On and got them out. Turns out the drive is slightly larger than 1/4” so my drive wouldn’t work. The marking says SM 8 and the other one I saw said SM 9. They seem older and thought I’d ask if any of you know about these and if they had a specific use. I figure they may have been made for the military or maybe for a metric drive? Thanks for any help identifying them...

 

[plinker]

9/32 drive, an odd ball but not the only one, there was 5/8 drive as well.

Some history,
http://alloy-artifacts.org/so-early-sockets-p4.html

 

[MJOPE]

Got it. Thanks for the link. I’ll take a closer look for the date code. I appreciate the help/info...

 

[Downwindtracker 2]

I got a J H Williams flex head that was a 9/32 but was ground down to 1/4"

 

[MJOPE]

Interesting. I’ll keep a closer eye out for this size. Thanks...