-JdK- This 1929 CS1 OF166 featured on these pages before but this is a much better photo. The pic was sent by Paul d'Orleans; it comes from one of Stanley's personal photo albums.
Interesting pic; it confirms this particular CS1 had a 7" Horton front brake and what looks to me like a matching rear wheel; the spokes are fitted to the drum, not the hub. The oiltank is much larger than standard.
-SG- This photo surely shows the right hand angled inlet port - perhaps as the 'Gardner' engine head though not really possible to do a fin count to see if it has the 'raised ports' or not. And Stanley's smile - is that a missing tooth - lost in his prang in the '29 TT? If so, it helps to date the photo a bit.
The scan below (From MotorCycling, June 6, 1928) is not really relevant except to show the brake arm set up on the works bikes was different to the production version. It further shows the larger oiltank used on these machines.
