keyless chuck removal problem

Hi there,

My chuck has slipped badly in this tool almost since new.
Finally decided to replace it with a jacobs professional grade .
Could not find a tool that would loosen the chuck retaining screw.
Looked like it was just round and damaged from all of the bits that had slipped
over the past year or so.
Decided to order new drill DCD791 because I like the feel and power of this series.
Looked inside the chuck and there is just a small round hole in the center the screw….
Looks like no torx, no allen, no flat, no nothin”!
Any idea of how to remove this factory chuck so that I can install a good one?
Happy to make a donation here!
Thanks in advance!
RC