In the scene where Michael Caine's character is packing up to leave, he is packing his belongings into his suitcase, so I would assume that he is packing up his room. But, when he finishes and walks out the door, he pauses outside the door, and we very deliberately see the room number. It is 103, the same room number we've been shown several other times earlier in the movie to be Sandra and Miss Texas's room.