h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Forgive me if I'm wrong, but the alternative names for shillings are:

60/-: Light (akin to English Mild)
70/-: Heavy or Special (akin to English Bitter)
80/-: Export (akin to English Best Bitter)
90/-: Strong (akin to English Strong Bitter)

Don't ask for a heavy and expect a Caley 80/- by any means, you'll probably get given Tennent's or Tartan Special.

Also, it should be pointed out that IPAs used to be a bit stronger, also to help survive the journey, until Caley made Deuchar's at 3.8 % abv, and promoted the idea of a light, refreshing quaffable session IPA, prompting other breweries to bring out similar products. American microbrewers usually stick to the stronger original style.

The reason for calling the beers by shillings is that was how much tax was paid on the barrels of beer as per the strength of the brew inside, and chalked on the side of the barrel to show that the tax had been paid.

At one time there were over 30 different breweries in Edinburgh and it was far simpler for the punter to ask for the beer by the strength of the beer as denoted by the chalk marks than to ask for the brand or name of the beer.