This is something that I have had to deal with on numerous occasions. Oftentimes, people like to clean out their attics and bring all of their old, unwanted items to museums. To them, they want to see the items go to a good home, and often cannot bring themselves to throw the items away. In a lot of cases, these same people do not want to be bothered with paperwork, and simply want to make the change in ownership fast and effortless. If your institution has decided to accept these items into your collections, I suggest that you go ahead and begin the process of accessioning them. You can always assign the items a temporary accession number and properly store them. If your institution does not want the items, keep the items for at least six months, in case the donors come looking for them, and then dispose of them. In both cases, I would attempt to contact the donors, and let them know how important a signed deed of gift is your museum as a legal document. One book that is good at answering these sorts of questions is Rebecca Buck’s Collection Conundrums: Solving Collections Management Mysteries.