I've mentioned Richard Frajola's estimable PhilaMercury website before on this blog. A recent addition to the resources section are pdf's of 35 articles by Edwin Mueller originally published in the Mercury Stamp Journal between 1950 and 1961. Unfortunately, the author's death in 1962 prevented the completion of the series, but we are fortunate to have coverage from Alsace-Lorraine through the Netherlands.
A couple of paragraphs from the introduction will clarify Mr. Mueller's focus:
"[The series] is written with the intention of showing that there are many ways to collect and that there are many countries in which the classic stamps can provide the most satisfaction to the specialist. The glamor of new issues is advertised in the philatelic magazines in a way that makes the good old classic issues look like poor relatives. It is high time to show the lure of the classics, to give the collector a vivid picture of the glamor which lies in the stamps which are seventy five and morc years old and were produced and used for postal purposes only, without any intention of making them items for a stamp collection. "
"In writing about the classic issues of tbe European countries—to which we have limited our nevertheless quite extensive undertaking —we want to show the collector the possibilities which exist in this field. We want to tell him what has been already achieved in philatelic research in the various countries and where fertile fields still remain to be harvested. We want to give information about tbe possibilities of specializing and give hints about the difficulties which may discourage the collector who wants to assemble a specialized collection. We will show the fields which are so hopelessly barren that we would advise keeping out of them. We will not give any advice as to which stamps may prove a good investment, because classic stamps, bought with knowledge and alertness will preserve their value, giving to the collector the enjoyment of his collecting as a dividend."
I should note that most of the articles were not illustrated. (Thanks to Keijo for letting me know there were some illustrations.)
Here is the link: http://www.rfrajola.com/msj/msj.htm