Super Bowl Footballs: Game Used vs Replica

[fredskinz]

Is there an easy way to tell the difference between a Super Bowl game used football and one that was made as an authentic replica? I know about the date letter codes, but are there any identifiable features to a vintage game used ball? Obviously, I'm talking about unmarked used balls with no referee markings. Thank you.

[volunteer]

Any game ball from the early 80's on will be marked by the ref.