Hi Rod,
I see what you mean. You might be able to get a better idea by taking a rubbing of the plate. (Paper and scribble over it gently with a soft pencil).
Don’t get too excited about available information. Factory records were destroyed when they closed the Slough factory. There is still, thank goodness, a wealth of knowledge within the club and elsewhere. French production is, apparently, much better documented.
Good luck. Let me know if I can help at all.
Roger