It starts off by saying...
"Talking to the experts, it quickly becomes obvious that every single feature of a stamp needs to be considered separately before a judgement on its overall condition can be passed. So this article will look at each of those features individually, before drawing them all together and attempting to assess how much more than catalogue price a superb example might be worth and, conversely, how low a price should be put on one of lower quality."Gum, margins, perforations, tears, creases, perfins, toning, cancellations, and postmarks are all discussed in an updated version of a series of articles first published in Gibbons Stamp Monthly in 2003 under the title of “Defining ‘Fine" which also appears in the introductory section of Stanley Gibbons’ 2011 Commonwealth and British Empire Stamps 1840-1970 catalogue.
To read the entire piece, click here.