I have an example of the longer model, a 1251A that's 13" long. It looks like the prototype was made by sawing the chuck of a 251A and splicing in a 3/8" rod to make up the length; North Bros. then made a prettier version for production. For some reason, I'm having trouble bringing up the scanned North Bros. catalogs that can be found here and there on the interweb; but if I recall correctly, the 1251A was marketed for automotive mechanics particularly.
Picked up, missing its cross handle, at a junk shop for a not scary price, because it was too cool to leave there. I have no idea if I'll ever find a use for it - but if I need to tap a hole in a deep awkward spot, I'm ready!