Help...what is this?

[mklotz]

It drills properly sized holes for wood screws. The smaller diameter at the tip forms a hole for the screw threads, the larger diameter forms a hole for the screw body, and the flare at the top forms the countersink. I've never encountered a #9 screw so I suspect that it's for sizes 6 and 8.

I have a complete set of this flat style drill bought at Sears years ago. They still work but have been superseded by more modern versions that use a real twist drill and an adjustable collar that allows one tool to work with any length screw.