Enchanting a Ring

What constitutes a "ring" in the Shape and Material bonus table for enchantements?

I always thought of finger rings whenever I read that, but would it not also include a circular bracelet/arm ring?
Probably even an ear-ring (assuming it is circular). And a nose-ring (for cattle and camels).

A wheel with spokes might not count, but what about the iron bands that coopers use to hold barrels together?
Does the "ring" need to be an unbroken circular band, or could it have two ends that have been closed together?

What of a circular groove in your sanctum's stone floor encompassing your lab, the groove filled in with lead. Could you enchnat that lead circle as a ring?

Otherwise, have a happy new Year (Gregorian calendar)
Dale

Yes

Probably

Undefined. Personally I'd require that it be closed - symbolic of continuity and thus constant effects.

Yes.

Likewise.

I don't have the books with me right now, but I seem to remember (and this may have been in 4th ed) an example character that carried a closed circular chain with warding spells enchanted on it that activated when it was laid out that constituted a ring. This may have only been for spell purposes (target and duration), but in my saga I would allow it to be a ring for the purposes of shape/material bonuses. I would see anything that you could carve and use as a ring duration or a circle target to sympathetically constitute a ring in mythic Europe.