Don't rely on this picture as a definitive " how it should be". There are one or two parts from different model years that are not strictly correct, but even so it is a well presented bike.
Shows a typical worn stand, lying a bit too low for easy operation, and the very close run of the silencer against the lower frame member.
Started life in Scotland, if the plate is original, SJ is Bute area, or its a re reg with a period number, UK DVLA supply unused Scottish area registration numbers for historic vehicles brought back to life, or built from mainly original parts. How clever is that?
Seems I was a bit critical of the production welding in my initial post, so sorry for any distress caused to any welders out there, I just got it wrong.
As to whether the leg in question is from an A7 originally, the answer is maybe. It is a part used on various models in the range at the time of production, and it depends on what front brake was fitted to the forks in the factory. 60 plus years later, 17? owners......anyone's guess. Could have been original, or from any of the models listed by Julian.
Be careful sourcing one on eBay. Some sellers don't know the finer detail of the variants and list the application incorrectly. As the fork bushes and oilseal holders are common, the unwary only find the mistake when the front wheel won't fit....damn, they say, it must be for an Ariel Hub!
Cheers
Swarfy.
Additional. Thanks to GB for drawing attention to the safety critical adjustment of the doo-dab.