I keep a spreadsheet of every train I've seen since I was 13. Recently, I went to New Jersey to railfan on the busy tracks operated by New Jersey Transit. While there, I saw Amtrak ACS-64 #638. This might ring a bell to some who know that 638 was recently wrapped in a Harry Potter paint scheme. But I saw 638 before it was painted. Just in normal ACS-64 paint. In my spreadsheet I keep track of if an engine was a heritage unit or not so my question is: If the engine wasn't a heritage unit at the time, but became one in the future, do I mark it as a heritage unit?