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

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 old versions 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? Thanks, Don.