I found an interesting research tool for old callsigns recently while trying to find some information for a friend.
HamCall.net has online callsign archives for the years 1921, 1954, 1960, 1969, 1983 and 1995 to present.
You can easily construct a URL to look up a callsign in a particular year as shown below. In the example below, I am looking for the address of my Elmer, Dan Sullivan, WB2PED, in the 1969 archive:
If I wanted to check in the 1983 archive, the URL would look like this:
I even found who held my callsign in 1960:
This is a good resource if you know the callsign and the year.