The owner of No. 429 send us this nice message, where we found out it's No. 415.
"I came across this picture while searching for pictures of Citroën SM in my archive. It was made in April 1982 at Citroën dealer Roques in Alencon. At the time we were looking for Traction Avants, but I thought this peculiar car was worth taking a picture as well. Unfortunately no number visible, but maybe the registration number will help you. This M35 was in a good driveable condition. I didn't know I would encounter mine a year later...."