Quite so, GB. Looks to be the open top crankcase version.
Hi J.S. Get the vacco on it and send in a few pictures. Congratulate yourself on a reasonable find. Looks to have been dry stored, which helps. Ask the vendor if the correct front wheel is available. Can't make up my mind whether the fork legs are clamp on or earlier screw in spindle or even Ariel type. Whatever, the front wheel is the single sided type, with the better brake, but not strictly correct for the model year. Frame and engine numbers can confirm model year for now.
There must be a back story of how it came to be partially dismantled, even down to the missing lower fork yoke clamp bolts. Any papers or reg no? Keep us informed, I think it will be a journey of discovery.
Get your cover story rehearsed for SWMBO, and arrange long term finance.......
Welcome along.
Swarfy.