I had taken a 7 day cruise 40 years ago. I found a picture which included a Carnival waiter with his name tag. I was given full credit for it. I provided the ship, year, month and port I departed from. It was very easy.
Let me also add that when I did a Mediterranean the days were so long that we rarely went to the dining room, so I didn't have to change. Most days we got back so late and were so tired, no one felt like going to the dining room.