Awrite, guys. Take it outside...
My scam comment was only in hopes of bringing a little levity into the discussion. :roll:
I think Sisyphus nailed it. Dunhill group sizes are probably most helpful to those who already know them. Not as useful for someone who has not.
Maybe another context. Golf?
A Ping 3 iron probably doesn't have the exact same face angle as a Wilson 3 iron. But when someeone says "3 iron" it gives an idea of it's basic shape and use. Give or take. In other words, you know its a distance club versus, say, a wedge or 9 iron.
To argue that the numbering system is flawed and therefore useless since the two brands differ by a degree or two seems silly to me. They're just ballpark figures like with pizzas or soft drink cup sizes.
You tell me Group 3, I know it's a smallish bowl. Exactly how small I can't say, but I can gather that it'll suit me for flakes. Better perhaps than a Group 6 because I like smaller bowls for flakes.
"Hello Domino's? Yeah, could you tell me exactly how many milliliters your small coke cup holds? What? You don't know!? What the hell use are you!? Get me someone competent, please! *******!"
I don't think black and white is the best way to consider pipes. Just saying....