The Indianapolis Museum of Art has put up a searchable database of all the works it held "in trust" for the public . . . until it decided to sell them. (It's actually just a very partial list of such works -- from 2007 forward.)
I'm reminded again of a comment from MCASD's Hugh Davies: "We museum directors can huff and puff about how once we bring these artworks into our collections ... they become this special trust that is the patrimony of our cities and that they're held in trust for future generations. It's B.S. We go on and sell them [and use the proceeds from sale to replenish the collection]."