Using the following criteria, you can determine yourself whether the collection you have inherited could be valuable:
Photo certificates or other kinds of certificates, frequently issued by the BPP (German Association of Philatelic Experts), can generally be taken as an indication of a professional collection. These certify that the individual stamps are genuine.
If the stamps are collected in illustrated albums, this also points to a more valuable collection. This gives a good indication as to whether the stamp collection is complete. First-day covers and first-day sheetlets, by contrast, are generally worth little or nothing.
If there are indications – for example, enclosed invoices – that the stamps were already acquired at stamp auctions, it is likely that it is a professional stamp collection.
Even if a collection might not be very valuable, its size may be a decisive factor. The best thing to do is to count or estimate the total number of albums.
However, it is ultimately the popularity of the collection field that determines whether a collection is likely to meet with high demand at an auction. Are the country collections from European countries, Germany or overseas? For instance, there is currently a high demand for Chinese stamps, meaning that these fetch high prices. By contrast, collections of stamps from the Federal Republic of Germany between 1955 and 2010 tend not to be of interest. If the euro collection extends until 2014, the postage values of uncancelled euro nominals tend to sell well.