Wierd drill bit or maybe a reamer?

[bas157]

Got these at a yardsale this weekend. Look like some kind of weird drill bit or reamer. Any idea what they are called or if they are designed for a specific purpose? I haven't seen anything like them before.
Thanks

 

[Air21]

It's a zero flute countersink, that hole is barely offset so it's great to deburr holes or cut a nice chaterless countersink

 

[bas157]

Thanks!

 

[Ign]

Those are spendy new. Nice find.

 

[DHCrocks]

yeah its a countersink. I have one and its much better then the fluted types. it leaves a clean hole with no chatter. I use it for countersinking holes in wood as it leaves a clean hole.