Tom Riddle Memory

In Harry Potter and the Half-Blood Prince, Dumbledore reaches for a Tom Riddle memory dated 1938. He tells Harry that this was the first time he met Tom, but to the left, there is a memory labeled Tom Riddle that is dated 1937. It is most likely someone else's memory relating to Riddle terrorizing two children in a cave at the seashore, which is described in detail in the book.