Agricultural museums collect and preserve objects (sometimes including living collections as well as historic structures and landscapes). These objects become the basis for educating the public. The best collections document makers and users of those artifacts to establish provenance.
Museums do not capitalize their collections. In other words, they do not trade in artifacts. Ethical standards prohibit museum staff from trading in objects. AIMA does not connect sellers of objects with potential buyers. Instead, AIMA encourages individuals with items that they believe a specific museum might find of interest to contact the museum directly.
For more about the definition of “museum,” see the ICOM codes of ethics: http://icom.museum/the-vision/code-of-ethics/
See also ICOM ethical standards for acquiring objects: http://archives.icom.museum/acquisition.html