Loads of good honest information ( and some beautiful guns) here! Canvasback and Saskbooknut both make some very knowledgeable points. To many Americans nothing can compare with American guns of any type and they will pay far more for a simple rugged farmer's tool than the actual quality warrants. Remember that many classic American guns ( and some British and European guns made for the American market) frequently have excessive drop around 3" which won't work for most modern shooters. Of course, it still compares favourably with the horde of cheap Belgian hardware store guns they mostly have for comparison but above all Americans are patriotic, especially about AMERICAN guns. If you buy into this market you are overpaying compared to the true value of the product and are competing with your American cousins - using American dollars. If you are looking for a safe queen for investment purposes this could work for you if you spend enough to get a minty original example of a higher grade gun but the buy in is very high - do you want tens of thousands tied up in your safe while you do your shooting with a Browning or Beretta? There were many very high quality pre war doubles made in Germany, Austria, Belgium, Italy and France but because all of these countries were mostly subject to war time confiscation and ravaged by war the survival rate is very low making really good examples hard to find unless they were imported into the USA or Canada prior to the war. If you can find one it will likely have an unfamiliar name but because of this lack of brand name value it can be a stunning value.
The British made very fine guns between 1900 and 1945 with tens of thousands of survivors and even the plainest guns by obscure makers were beautifully made, very rugged and pure pleasure to use. Thousands of these guns came to Canada with British immigrants and retirees between 1920 and 1990, many in outstanding condition. The ones you want to look for will be the heavier waterfowl and pigeon guns, at 7-8 1/2 pounds they will be heavier than the regular game gun and built to take a steady diet of heavy loads. Look for recent proof marks showing 70 mm ( 2 3/4") or 76 mm (3") , previous generation marks showing 2 3/4" or 3" or the earlier marks of 1 1/4 oz (2 3/4"), 1 3/8 oz, 1 1/2 oz, 1 5/8 oz and even 1 3/4 oz, these latter designating 3"" or longer chambers. These will usually be accompanied by a stamp on the barrel flats showing LC enclosed in a diamond denoting long chamber. Make SURE that the chamber length matches the chamber markings, DON'T buy a gun which has had the chambers lengthened without being suitably reproofed. Why? Worthless anywhere except USA and Canada, can not be legally sold in UK or European countries and a very dubious investment as well as being potentially hazardous. You will pay more for a famous name like Westley Richards or Holland and Holland but hundreds of others like Greener, Ford, Hollis, Lewis , Bland, etc made the kind of gun you are looking for in various grades with excellent quality. Check the Bland website in USA, Chis Batha there specializes in turning up the kind of gun you are looking for and also Vintage Doubles in Wenatchee Washington. Ellwood Epps and Prophet River in Canada get a few from time to time. Haunt gun shows, talk to anyone displaying fine doubles. Remember, always buy the gun, not the name.