Jacqueline de Ribes Cocktail Dress: How to Sell?

From my downscale shopping in Paris in June . . .
to upscale shopping my closet

HELP WANTED

 Many years ago, I acquired a Jacqueline de Ribes dress at one of my usual venues. I knew the name--probably from reading Vogue in the 1980s. (My memory was a veritable storehouse of miscellaneous info. Alas, not so much for recent things).  The dress had lingered for many months unsold. So I finally bought it. 

There's no size in it, but it fits Miss Em. She doesn't want it, not having a J de R lifestyle.

I first tried to sell it a few years ago. I had read that Didier Ludot, the famous Parisian vintage couture shop, was having a LBD show. I emailed a pic  and asked--in French that was corrected by Mr FS--if they would be interested. As usual--no reply.

Yesterday, I picked up an Architectural Digest from the FREE BOX at the library. Newest issue. I discovered that The Metropolitan Museum of Art is having a J d R show, featuring both her own designs and the chic stuff she wore (People with that caliber wardrobe don't follow the Kondo decluttering program--or I guess they love everything). 

So here's my question: how do I sell it? And for how much? It's the twin of this one, offered for $950 on 1st Dibs.

Thanks for any advice.