Have you tried the "File" tab and check e-file status?
Of course if you made a duplicate copy of the file you filed with then it should not matter which one was the actual file since they are identical duplicates, but if you modified one after duplicating then you would have to determine which one you modified. (A Mac has date/time created, date/time modified time stamps).
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
