View attachment 233690 These are kennametal dcknr-205d ins cn-54 holders. The d means a kenclamp system but it does not look like that to me in the drawing. It looks like a Kenloc to me.
Page #4.
https://www.kennametal.com/content/dam/kennametal/kennametal/common/Resources/Catalogs-Literature/Metalworking/Master Catalog - Inch Sections/A-11-02679_MasterCat_stationary_toolholders_inch.pdf
It just dawned on me, I bet whoever used it before loctited the clamp.