Yes, it is an E29. Points differing from the previous year E28 are the saddle tank and the oil sight glass sitting on a corbel of the timing chest cover and facing rearward where it was probably easier to view, rather than being built into the timing chest cover and facing outward. It would also have a push-pull petrol tap, but you can not see that. I seem to recall reading somewhere that wired on tyres were an option on the E29 (First year available on a Douglas? Definitely in 1930.), and it does look like drop center rims are fitted here. The F29 would be identical, except for having foot rests instead of foot boards. 1930 saw the first of the S6 models and the end of the E/F models that began with the 600EW. Looks like the owner splurged for the optional twist grip throttle over the standard levers, and paid the extra £6 5s for the BTH lighting set.
-Doug
