CP's list is useful as a guide to the beginner. However,once you specialize on a type or series key dates or rarities take on a new meaning. The 1D boys are all chasing a market which is well documented and every Tom,Dick (but not Harry maybe) can easily track down, hence inflating prices. I still chip away in areas that I know (price guides can be hung in your privvy). Incidentally I've just ordered an Edward 1 penny which if correctly described would/could/should be worth 2 fold. maybe more ...not that I will be selling soon.