It is an old 1/2" female ratchet with no spring. Mine is an orphan based on the 1927 Hinsdale patent. It works on a rocker system to engage the teeth.
http://www.google.com/patents/US1650085
http://www.ebay.com/itm/Vintage-Hinsdale-S-15-Ratcheting-Inch-Box-Wrench-USA-/232113233268?hash=item360b06dd74:g:zZEAAOSw0UdXv3qX
I am sure you old hands are familiar with it, but I had never seen one like it.
Mine is more substantial than the one pictured. Again, it is 1/2" square drive. It is 9 1/2" long; the business end is 3 3/8 X 1 9/16". It has a heavy cylindrical knurled handle.
It came with a (similarly unmarked) 3" male to male extension instead of a plug.
Anyone here ever seen one or know anything about it?
I had one similar that was SK and have seen the same one unmarked.
Boom! That is mine. Unmarked, as is this one from AA, but was found in a set with an
SK decal on it.
The only difference is that mine has 2 3/8" of continuous knurling instead of the three bands as in the picture.
Thank you so much!
https://www.google.com/search?q=vintage+SK+ratchet&biw=1280&bih=570&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjVyIDAnZjQAhWDXiYKHfeoDsgQ_AUIBygC#imgrc=MKhT4uY7MPu0iM%3A
I'm pretty sure that I have a couple of these in a bucket somewhere. Unmarked.