This popped up on Ebay in 2013. It’s a quick change box for a LittleJohn MKII. Fortunately it came with a leadscrew, feed shaft and a bunch of bits around the changewheel end
Mounting the box meant having to grind away some of the lathe bed, making scallops to clear the gears. I put some time into making the box as short as possible to get the carriage as close to the chuck as I could.
I had to extend the back gear knob to clear the gearbox
I mostly use the gearbox to quickly change feed rates. If I’m screwcutting, the gearbox is usually set to a ratio of 1:1 (left lever on B, right lever on third slot from right)