"There is apparently no prohibition in the US from any of us hanging out a
shingle and saying we are a "museum."

I am under the impression, at least in New York State, that "museums" are
regulated and certified by the Board of Regents who are appointed and also
oversee the State Universities and Colleges. I've not read of any particular
cases but have heard of some certification issues.

(Walter Creonkite is an "Overseer" of the National Maritime Historical
Association, based in Peekskill, NY)

We have a local chapter of the NY State Arcaheological Association, in
Southold, NY on Long Island, across the street from the Custer Institute
(astronomy) which was endowed by a stock portfolio donation, therefore it
exists, in its own building! I heard that there were so many "artifacts",
they were "curated" in the back yard in bushel baskets when storage space
inside ran out. (Johanneman, Schroeder, pers. comm., ca. 1980). I'm not sure
an issue like that gets to be evaluated for breaches.

George Myers