The maker ESW is not listed at present. Still, we know your English brooch is sterling silver made after 1890 and properly assayed (guaranteed Sterling quality).
These types of hand carved shell cameos were very popular until about 1920. So we can date it 1890-1920.
The estimated retail value is $750-950.
Online auctions like eBay generally bring wholesale selling prices. Sales in the eBay "Buy It Now" format are closer to retail.
If you would like to sell close to estimated retail, some ideas are:
The internet has your largest audience of buyers. Place small ads on these sites or set up your own small store on these sites.
Be sure to specify local pick up only for large items. That way the buyer would be responsible for obtaining his own insurance and transport.
These sites carry antique as well as vintage items.
Accept PayPal only.
Etsy.com - small fees-20 cents to list plus 3.5% final price.
These sites are excellent and more upscale but fees are higher. I only recommend them if you have several items to sell.
Or your nearest CraigsList.com where you can list items for free. Accept cash only.
Ultimately, to obtain these retail values we assume the piece or set is in good condition and that the final value depends on sale geographic location.
In general, a private seller to a dealer, via consignment or at auction can expect 30-50% of estimated retail value.
Insurance replacement values are usually about 20%-50% more than retail values.
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