dont know what year it is
Have a look in the inside of the bed casting at the tail stock end. It will have a casting date (month/day/year).
Looks like a 415 to me, but I'd be guessing. Everything you want to know about an SB in on Steve Wells site here:http://www.wswells.com/
He collects the serial numbers, so while you're looking at the end of the bed check the serial number (usually stamped at the top front side at tail stock end) http://www.practicalmachinist.com/vb/south-bend-lathes/serial-numbers-wanted-128483/