There are a couple of possibilities. One is to try Info -> Audit Trail. This gives a list of the last change dates by username, although I think sometimes it can clear itself. The other, if you have two models you suspect of being copied, is to look at the Feature ID (FID) of similar features in each model. Unless two people model the same part using exactly the same sequence, it is unlikely that all the FIDs will be the same between models - so if several FIDs *are* the same, it suggests that one model has been copied from the other. Dimension names (d123 etc) could be another clue. HTH!