Thanks for the thoughts on this bullet. I do agree its not a Cosmopolitan II, but if it had the characteristic flat nose of the Cosmo, it is a dead ringer for one of those pictured in Tom Stelma's book. Tom mulled over this bullet for about a half hour, took a bunch of photos of it, and after about a week, called to tell me he concluded it was more like a Cosmopolitan than anything else he could find. I tried to take a better photo of the cavity - it is attached. The base is not carved - I am certain of that. The air cavity makes it difficult to tell what type base cavity it has, but it is a very deep plug or very deep slight conical cavity. I studied every Sharps I have pictured in all the bullet reference books - and the base simply does not come close to any of them. The next time I have the opportunity to be with fellow leadheads, I'll bring it along