Him or Me (1930)

Prince Valona has a bit of trouble with his girlfriend Eveline (Olivia Fried), so he's quite open for the attraction of a young lady he meets by chance (Valerie Boothby). He doesn't know, however, that this lady is a detective who follows the con-man Carlo Moreno, and as the prince and the criminal look alike, she mistakes the prince for the criminal. The real Moreno isn't far away, though, and he first deprives the prince of his train ticket and then also takes on his identity in order to steal a pearl necklace from Eveline.