What type of tool holder is this?


I am trying to organize my lathe/mill tools and came across this tool holder in a box of older tool holders I purchased decades ago. I don't seem to be able to identify the type and what it was used on.  At first glance it looks a bit like an R8 but physically not the same.  Anyone know what type it is?
No application for my SB9 or any of the fixtures/tooling for it. My vert mill is R8 and my horiz mill is one of the Atlas MFCs.

It is 4" long and the big end is 1.45" dia with a 1/2" hole in it. I assume for a 1/2" inch shank milling cutter.
The big end of the taper is 1.18".
The draw bar is 1/2-13.
The outer threads are 7/8-24.
The shaft is 0.8" dia and 3" long to edge of taper.

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