by pacomotorstuff » Thu Dec 22, 2016 8:17 am
Pre-unit construction, so 1964 at the latest.
Looks like an A10 variant.
Single carb, so not a Lightning Rocket.
See if this helps:
A10 GOLDEN FLASH DA10 13201 GA7 11101 650
A10 GOLDEN FLASH ALTERNATOR DA10A 13201 GA7 11101 650
A10R SUPER ROCKET DA10R 3001 GA7 11101 650
A10S SPITFIRE SCRAMBLER DA10SR 401 GA7A 401 650
Columns 1, 3 and 5 are what you are interested in give engine, frame and CC
Try motobrit.com for more info - where the serial numbers came from.
Haven't looked at one of these since I was a kid, but your fuzzy photo shows a bike in pretty good shape - at least, aesthetically.
Have a Very Merry Christmas (especially if you've bought the bike!) and a Happy New Year.
Pat