We're all just guessing here, but since that is a belt drive headstock, it doesn't have all the shafts, bearings, gears and shifting mechanisms to add to the weight, it doesn't appear to have a QCGB, so there is a few more pounds off.
It's still a good sized lathe, and a lot of cast iron, built back when they were meant to last. Since it has a middle support leg for the bed, that gives another clue. I may be on the heavy side, but I would say 7,000-7,500#. Can't see if it has a taper attachment. That would add a couple hundred pounds once it was mounted and all modifications made to fit it. No steady rest, so knock off some. It's really hard to guess.....especially not knowing who made it. Some makers went out of their way to make a heavy, rigid lathe, and some went in the opposite direction.