Every country has sub specialties that are avidly collected by internal collectors, but which foreign specialist collectors of those countries never really warm too. As an auctioneer you can see this in bidding patterns and where certain stamps eventually sell to. Ordinary Great Britain stamps in our auctions sell to Americans, Canadians, Britons and Europeans. Plate numbers and cancellations of GB are similarly collected worldwide. But specialized phosphors or graphite lines on QE II and Machins always seem to go back to Great Britain. France has a world following, but the precancels, which are so popular in France itself, are relatively uncollected elsewhere. And the Germans? Well no one else enjoys counting perforation holes or measuring paper thickness or booklet combinations the way they do.
 
US philately's big national skew is plate blocks. US stamps are either the second or third most popularly collected specialty in every country besides our own (US stamps are #1 here). In all other countries the list goes like this -the home country first (for instance, in France, the most popular specialty is France-in Germany it is Germany) followed by either British Colonies or US in differing order depending on the country (for instance in Japan, United States stamps are the second most popular specialty behind Japan, and in France, US is number three behind France and British Commonwealth). But nowhere except here do people collect plate blocks. It just doesn't make sense to them and not coming out of a collecting tradition that esteems marginal markings there is little appreciation of them. Currently, there is an American stamp dealer of Chinese descent who is a large buyer of United States stamps at auction. Other stamp dealers, being a gossipy bunch, had wondered where he was selling all of the US stamps that the was buying. When they realized that he never bought plate blocks it became clear that he was sending hundreds of thousands of dollars of better US stamps per month back to China for their market. Nice exchange for our iPads.