Fine bit of folklore, that thing about glass bottoms and the King's Shilling. I think it's a bit more practical: with a glass bottom you can see if the beer is cloudy.

I once had a smooth, nickel plated tankard. The beer went flat in about 5 minutes, not just lost its head but it's entire condition, and tasted like drip tray slops. Any physical chemists with views on the bubble- forming activity of nickel?