I'll throw this out there.
I think the OP, Claycrusher, is looking for a way to determine grades of English guns comparable to the grading systems used by American makers of the past as well as other makers, a marked grading system either by model numbers or grade stampings. Examples would be Parker letter grades, Ithaca numerical grades and the model numbers used by Sauer, named grades by Lindner Dalys. Also, as mentioned some makers assigned different serial number groupings for different grades.
Generally speaking, other than a letter from the maker stating the grade of a particular gun, there is no way to define grades of older English guns. As you can see from the varied replies and disagreement above, it is highly subjective.
It's been said Purdey only made Best grades, does that mean they are all of equal quality? What is Best to the seller may only be Second or Third grade to a buyer.
