Zut Alors! How on earth did I miss this one! I thought it had been solved a long time ago
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I remember this drawing well, as it was used on as the lead image on the cover of a newspaper that Ligier was handing out at the 1999 Paris Salon.
I probably do have a photograph of it somewhere, but as it was the pre-digital camera age, it might take me some time to find it. When I do, I will be sure to add it here.