Larry gave a great description.
That was a very nice lathe when it was new! Cataract with thread cutting (chasing) capability on a steel stand!
And as Larry alludes, looks to be 5c when most were 4c?
The back T-slot is for a chase threading attachment.
Unfortunately unless you get lucky at out-of-the-way auctions, tooling one up is starting to become expensive.
Lots of tooling around and on ebay, but prices keep advancing. People tend to buy the lathes, sell off all the tooling, and then dispose of the bare beds, which bring the least money and are most effort to dispose.
I've got 2 with chase threading, but both are 4c spindles.
Scroll down about mid page here on Tony's lathes site:
Catarcat Lathes
What is with the forum software that actual pic's can't even be pasted as attachments???
smt