Admiral didn't announce plans to make color tubes until August of 64
https://books.google.com/books?id=GU...istory&f=false
So, that roundie probably had an RCA tube (sulfide phosphors, you can tell by the screen color) and might actually be a long-lived one. Admiral-built color tubes had a poor reputation. They offered a 3 year warranty on their CRTs (not including labor), and apparently it was needed.