This is what my AT300/1220 looks like. mine Looks like a solid nut with the typical slot and tension screw to take up backlash. Except, on this nut, the lever that’s visible can reduce backlash or lock the carriage in place. Seems to work ok.
I know people don’t like these machines, but I just used the lathe on mine again a couple days ago and it’s pretty decent, for what I do. It will definitely take heavier cuts than my SB9, with less chatter risk. And I can make pretty accurate cuts. I have not used the power feed as the gears currently in place seem to be for a course thread of some kind. The carriage hauls a** when i engage the power feed.