I have no real idea of what the phrase "Limited Editions" means. There is a perception by the public that they will buy something rare ... limited to "ONLY xx number of copies". However, the "limiting" can easily be interpreted in a number of ways; as "ONLY 25 Prints will be made at the hands of the photographer'", or "ONLY 25 Silver Gelatin Prints will be made by anyone - reproductions in other media may be of any number," or "Only 25 Prints will be made in this run."
What I have seen of "Limited Editions": Signed by the Photographer/ Artist, and numbered, "xx/25". That signature and the expressed intent of "no more" sanctioned directly by the photographer, should be sufficient (IMHO) to define a "Limited Edition".