[Boost-users] [Serialization] Writing an old version of a class

I apologize if this is a duplicate posting. I sent this 2 days ago, and it appears in the archives, but I never received it back from the list and there have been no replies, so I am posting it again. Using boost serialization, I would like to be able to write an old version of a class, so that I can save data in an "old" format to allow other users with an old version of my program to read the file. I see from the archives that this has come up before, and Robert Ramey indicated it was doable and on the todo list, but I don't see it in the release notes or documentation. Did anything every come of this? Or, has anyone else done this? Any suggestions on how to accomplish this? Thanks, Don