Each node (the IPublishedContent type that most page types will inherit from) has both a unique Id (generally 4+ digits but not always), e.g. 1234, represented as an int. They also have a unique Key, e.g. 12345678-1234-1234-1234-123456789123, represented as a System.Guid. Either of those could be used, probably the Id based on your example.