What Can Be Done: Hamburg was and is one of the most populous, active, and commercial cities in the world. From the Middle Ages onward, Hamburg, through its membership in the Hanseatic league, was involved in and had a controlling interest in North Atlantic trade. Because the communication needs of such a significant city state were so great, there are few rarities among Hamburg’s 26 postage stamps that were issued for the most part in the decade of the 1860s, before confederation. Most Hamburg stamps follow the pattern of other countries, where used stamps catalog and sell for lower prices than mint ones. But several Hamburg stamps are much rarer used than mint. The   value of the first issue catalogs $100 mint and $600 used. Such a huge differential in price encourages forgers. And when you add to this the fact that the stamps of Hamburg were mostly cancelled with an easy to duplicate bar cancel, collectors should only buy used Hamburg from reputable sources.
Completing Hamburg mint is a relatively easy task. Specialists often add used stamps and covers and sometimes pairs and blocks to their collections. Currently Hamburg is the second largest city in Germany, so collecting the stamps of Hamburg is a very popular specialty.
Specialty Catalogs: the Michel catalog is the final word on all German States collecting, though increasingly, the Scott Classic catalog has been adding more and more specialized listings and now make a credible alternative to Michel.
Specialty Albums: The Scott Specialty series is very good as are the three main German specialty album producers—Lighthouse, Safe, and Lindner.
Availability of Material: As one of the most popular collecting areas of classic philately, Hamburg is serviced by a large network of German and American specialty dealers. The stamps as they are listed by the Scott catalog are not hard to find. Specialists look for covers, blocks, proofs, and other specialty material which can often make a difficult search even if the price is not too expensive.
Expense: Hamburg is one of the least expensive of the major countries that make up classic philately, and this accounts for its extreme popularity. Mint, the entire country is only a few hundred dollars. Used can be a few thousand, so be careful buying used stamps.
Overall Grade: A