However, small museums, historic house museums and many science museums need only have three or four of the five parts. The entire policy should be reviewed periodically by the governing Board of the museum and changes can be made as needed. Every single museum in existence should have some form of acquisition policy, from the Smithsonian to the smallest local historical society. Obviously, the more complicated the museum, the more complicated the acquisition policy, but even the smallest museums should at least have a mission statement, a scope of collections and a loan policy. A tiny museum need not have an accession or deaccession policy, but it should know its purpose, what it owns, and what it will share.
Collections have different properties than museums, although they are often called museums.
A collection is basically several different examples of one basic item. Museums often end up as many different collections put together, but according to the AAM, a collection alone cannot be defined as a museum. Another characteristic of a collection is that it has no need of an acquisition policy. Often it's run by one person and perhaps his or her family. The collector knows what he or she wants and will be doing all of the purchasing for the collection.