I can confirm that the coupe Jupiter wearing 138 is the Jupiter that Jean Latune had built for himself, and he rallied it several times.
This event as depicted by you wearing 138 is the 1953 Lyon to Charboniere rally, the "Charbo" with the car crewed by messieurs Gay and Trollinet.
I am pleased to see this photo, new to me, showing the rear of the car, all I have are front and front/side! Well done!
Could you mention that my book is already published and available from Amazon and oters. It is called
"Jowett Jupiter Special Body - from Abbott and Beutler to Rochdale and Worblaufen". It is a big hardback book weighing a full kilogram!