Used phase 2 lathe quick change tool post tool holders 250-207 cut off tool holder 25205 what I think is a Morse taper number. Holder 250-204 is a boring bar tool holder 3/4 in then there is a knurling tool holder that someone has also welded a block of steel to. My guess is to use it in a different size holder or in a bit holder.

Three of them have their knurled knobs. The one knurling tool holder does not. Please look at the pics. A little dirty but should clean up.

Really nice with a little Scotch, Brite and WD-40.