^Yeah, the whole practice of reusing a registration number with a letter after it is not, by any stretch of the imagination, a normal one. Frankly it doesn't make a damn bit of sense to use it at all.
Well I thought it was pretty clever. I remember watching the TNG episode "Where Silence has Lease" and noticed how the Yamato had a registration number with an E at the end. Since it was a galaxy class ship, I always thought that the line of starships named the Yamato must have dated back earlier than the Enterprise. I was disappointed when they changed the registry from subsequent episodes because I always enjoyed little details like a letter telling you a lot about a ship's lineage.