Hello. My question is about program rollback and the management of archive compatibility : let's say I saved on object of type T with my program in version 1.35 => archive.txt. If I roll back my program to a previous version (let say 1.30), I'd like to check (without trying to deserialize for performance issue) if T in 1.30 has the same "BOOST_CLASS_VERSION" as the object saved in archive.txt. *In brief : is there a way to retrieve the BOOST_CLASS_VERSION of T stored in the archive ?* I read boost code, but I didn't find a "quite direct" way to do that. It seems I must get cobject_id_vector of basic_iarchive_impl, but all this stuff is private. Is their another non-intrusive way to do it ? (By non-intrusive I mean : only using the boost public stuff, or at least with a simple inheritance to get protected member of base classes?). Thanks in advance. nicolas.