Size of vintage lathe tool rest

I have a vintage (or just plain old) Montgomery Ward Powr Kraft Lathe from the 40’s. The stalk of the tool rest seems to be an odd size (larger than the replacements they sell at Rockler). I have looked at the OWWM site and found the lathe and the manual that Brad linked me to but nothing that references the size of the stalk (unless I missed it). Thinking I may need to weld one up from scratch as I need a short one for pen turning.

I guess I could use a pair of calipers but for some strange reason I never seem to remember this until I am at work. So, does anybody know what size this stalk would be??

-- Andy - Seattle USA