Just to bore people further with a ppd. The Gutenprint driver for my P50 gives the following main headings:

General
Printer Features Common
Printer Features Extra 1
Printer Features Extra 2
Printer Features Extra 3
Printer Features Extra 4
Output Control Common
Output Control Extra 1
Output Control Extra 2
Output Control Extra 4
Output Control Extra 5

If I was to drill down what is in "General", I get.

PageSize
PageRegion
ColorModel
StpColorPrecision
MediaType
, etc.

If I was to follow Page Size, I get a long list including,

Letter
Legal
Executive
Postcard
CD
4x6
5x7
A4