I just went through various SB catalogs dated between 1931 and 1967 and don't find any catalog numbers or model numbers anything like that. I did confirm that a 4ft bed on a 9" would mean a 9x28 machine. And if the "C" in the model number given means a Model C, then that means manual cross feed only.
From whatever little information I could gather from trawling the net, no one seems to know much about this particular model.
I am not sure if I am supposed to be posting links to external sites, but here is the CL ad:
metal lathe southbend lathe C9-10JR
nice southbend lathe 9 inch swing with 4 ft bed , model C9-10JR . with plenty of tooling ,complete with steel bench and 110 motor ,ready to work . PHONE CALLS ONLY PHONE CALLS ONLY PHONE CALLS ONLY
philadelphia.craigslist.org
If I am breaking forum rules in any way, mods may please either let me know (and I will remove the link) or deactivate/remove this link.
Thanks for going through the catalogs and confirming that this is indeed a weird one.