As a museum docent worker at two local museums, let me chime in here. I would NOT donate items to museums, unless you REALLY had something ground-breaking and historic. Ie.: spanish armor, or the gun Custer himself used, blah blah blah.
Because even though the museums accept a lot or all donations (so as not to be "rude" or "ungrateful"), yet most often they will never see the light of day again. Because I can tell you for a fact (as a museum worker) that they get SO much donations, that they simply can NOT display all of it. And once they've got a carefully designed museum layout, they are not going to perpetually go in and re-arrange things , cabinets, etc.... Museum strength , personell, budget, etc... simply don't allow. And if the museum was ALREADY laid out to show a story and theme, there has to be good reason to change things .
We have well-meaning sincere people come in donating odd-ball things frequently. And ... to be polite ... none is turned down. Stuff like "great grandma's sewing machine that she sewed on patches for WWI soldiers", blah blah. Or "an arrow head I bought at the flea market", blah blah
So some md'rs, to try to make sure they're not a victim of the "basement storage" phenomena, might try to make a stipulation of "Must be displayed" . Or "On loan only", etc... This too , in year's past, turned out to be nothing but a headache for museums. So they now do not agree to such terms. Now the items , if accepted for donation, must be donated with no strings. They become the property of the city. Why ? Well for example:
Someone 20 yrs. from now comes waltzing into a museum "demanding something back". They want the sealed cabinets opened up and their item back now. Or horror stories of the museum can't find something they claim was "loaned" 20 yrs. ago , so now lawyers get involved. Or someone comes waltzing in saying "my cousin or sister had no right to donate that family heirloom, so give it back", etc...
Or the stipulation that "must be displayed" seems innocent enough, eh ? Yet think of it: This is NOTHING MORE than the public's ability to "control what the museum can display".
Thus no, I would not donate something unless it's so stupendous that there can be no-other-reaction than the rush of the curators to have the urgency of "must-display" notion.