Welcome, sir. Actually you`re on the wrong side (this is a LED topic) but until one of our friendly Moderators comes by, I`ll help you out.
The main distinguishing features of Version 3.0 Arc-AAA are the Level-3 Hard Anodise finish, it`s not quite as jet-black as the older finish, having an almost charcoal-look to it in some lights. It is very hard wearing indeed. The knurling is a little softer too but it`s hard to tell without having old and new side by side.
Secondly the insides- threads and battery compartment- are finished in "Chemkote", a gold tinted coating that improves electrical conductivity and inhibits oxidisation- the result is less flickering due to contamination.
Finally the foam battery retainer ring is black, not grey, and a slightly more firm and durable material.
How do you tell just by looking at one in the packaging? Hmmm, well asides from the slightly charcoal-colour, it`s hard. Suffice to say that most brand new Arcs from the Arc site and may of the dealers will be the v3.0.