newshound laid this down on his screen :
Your description of 3 balls in deepening slots made it sound more like some
designs of freewheel to me (rather than a clutch). It's certainly true that
freewheels are usually metal to metal. As TNP points out there are also
various types of metal to metal clutch. Some use sintered bronze on hardened
steel multiplates (later Norton Commandos, I believe). You don't want steel
on steel to see too much slipping, unless it is in an oil bath.

This is/was just steel on steel. The three balls in the slots, are just
the means to force the clutch plates tightly together, via a coil
spring and bearing.