Dangerously good taste Tony! Rudge updated their features almost continuously, so the Multi in the image is certainly 1914 or later. You mention the foot-operated oiler near the front footrest, said to have been first used by Cyril Pullin (there's a famous Douglas name - 100 mph on his "S1" in the early 1920s) on the Rudge he developed for the 1914 TT. The first of these (in a mid-year catalogue Pullin won the the May 1914 TT) was a smaller oiler (and brake) pedal, and the side plates for the forward footrests were rather skeletal. The bike in our photo has solid sides to the footrests and the larger pedals, so I'd date it as a "1915 model" or later. Rudge presented a brand new 1915 Multi to the Science Museum, and it has these pedals and footrests. Re the square flip-top fillers: I would have said that the entire Rudge range used these from mid-1914 on, except that the Science Museum bike has a screw-on cap! The lesson is that not all bikes are ever exactly to catalogue spec. Period catalogues make no mention of choice of filler caps.
Now, back to Douglas before we get into trouble!
Leon