I don't think this ratchet ever was part of a spinner ratchet. I think those were only 3/8" and were forged differently than this one. It is just a regular 1/2" raised panel that looks like someone cut the handle off of.
Look at the pics closer and It appears that the plating goes over the "cut" end. That was more than likely a Factory mod or manufactured that way, possibly from a standard blank, but before the plating went on.
The odd "spanner" could be for a special fastener, or it might be for a similar piece with it's own extension to make an articulated ratchet.
I don't think there is enough visual evidence to say with certainty that it is a Craftsman, simply based on the toggle and general design, again these tools are made on contract, and it's not unusual for the same design to surface under another brand.
Craftsman has always been pretty careful about brand recognition so it would surprise me if this was made under the Craftsman label.