Determine Crit'Air vignette for France based on Swiss emissions code?

The car is diesel and has an emissions code of B5a but I can't see which Euro code number that relates to.

Have not been able to find a look up reference either.

Anyone have a clue?

The official website says that all the necessary information required to apply for the certificate is on your carte grise.
Try emailing them if you still can’t work out which category the car falls into?

Canton GE uses the same StickAIR as France. You can input the Swiss emission code and determine the correspondence. B5a seems to be “2”.

Don’t overthink it. B5a = Euro 5a. You can tell the Swiss are creative, they added a “B” for style or whatever.…eugausweis.pdf