I thing it's a shame that the uss Sao paolo in the seventh season of DS9 was renamed Defiant NCC-75633 ant not Defiant NX-74205-A
Actually, Sao Paulo carries Defiant's original NX-74205 registry since pretty much everything we see it in is just stock footage. Indeed, the original intention was to give it the registry NCC-74205-A but they had no time or money to make the change.
Also, timeship Relativity's registry was NCV-474439-G and its dedication plaque says "seventh ship to bear the name." Unfortunately, this is actually rather sloppy, since if that truly is the seventh Relativity the first would be NCV-474439-A as opposed to plain ordinary NCV-474439.