The sofa you posted was sold by MetroRetro of Houston and listed on 1stDibs and their website as "Harvey Probber style". Probably because of the similarities to this sofa in the first picture, which is listed by many sellers as a Probber design, though I didn't see any tags or catalog photos to confirm. Edward Wormley designed a similar sofa for Dunbar in the 50's, the model 4906A shown in second photo below.
Many Italian designers of the 50's had similar curved sofas as well. My guess would be the white sofa was a custom design or made by a small-scale manufacturer using some popular design elements of the late 50's early 60's. If you're trying to find something similar to buy, I would search auctions and websites using keywords Probber, Wormley, and Italian.
In my experience Metro Retro can be a little fast and loose with their attributions, but they did say "style", which implies they were not able to confirm a designer. Unless someone on here can nail down the actual designer or maker, I think you're fine listing it as "in the style of", "manner of', or "after" Probber.
Assuming this is the only item you're selling, I'd start with Craigslist and Facebook, since they're free, especially if you are in a major metro area. Then, I'd say Etsy and Ebay, listing them as local pickup but willing to work with third-party shippers like UShip. You could do Chairish, but they'll charge 30% if you have fewer than 10 listings. Consignment is always an option, but they'll take 50% in most cases. Sofas are tough to sell unless they are tagged and can be attributed to a designer like Kagan, Wormley, Nelson, etc. Good luck.
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