I would bet on there being a slot in the back, why, because there is light showing in the photograph.
Incidentally, the tang on Morse tapers is not intended to provide drive torque, that's what the taper is for.
I would be interested to find out how that tapered hole with a flat was produced, magic maybe.
Edited By old mart on 05/01/2020 15:12:46
Edited By old mart on 05/01/2020 15:15:22