My name is Nora. Thank you for sharing your family story and my condolences on the loss of your mother.
The original illustration art by Guy Arnoux that was created and used for the cover of the Parisian restaurant, Le Coo Hardi would carry an auction estimate of $1500 - $2500 on today's market. If sold through an auction house in Paris, it could potentially exceed the high estimate. This is likely not the number you had hoped for, as I have gleaned from your posting here, however it is based on the actual sale market. You may want to contact Tajan Auction house in Paris to inquire if they would have interest in consigning your original for you. Here is the link to their website:
I would be happy to look over images of your artwork for you, it does not cost extra to send pictures here.
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