First step is to know exactly what you have, then research what similar items have sold for. (search completed sales at Auction houses and yes, ebay).

Go to antique stores and look at the prices of like items.

You say you have flat silver. Is that sterling or plate? Big difference in value.
If you have sterling, some jewelry stores will buy it from you. Same with jewelry, a jeweler may buy the good stuff.

Once you know what you have, ask a dealer if they would put it in their store
agreeing to give a commission on what sells. OR you can sell on craigslist or ebay.

Funky, vintage costume jewelry sells well on ebay.

Good luck.

You may also sell on etsy it isnt quite as expensive ,google the sites and get a fair idea from other sellers site how much things are selling for.

Some vintage picture frames are bringing $200.00 a foot so use caution.

"Once you know what you have, ask a dealer if they would put it in their store agreeing to give a commission on what sells."

If you leave your piece with a dealer, make sure to get the terms in writing.

I once left a sapphire with a store owner whose husband worked with jewelry. I wanted an estimate of what it would cost to put it in a ring. He wasn't there so I left it with his wife in a brown paper envelope over the weekend. When I picked it up, it had been replaced with a lesser quality stone. I didn't realize this until I got home. I didn't bother to look because I had known this person for over 20 yrs and thought I could trust her.

Here are some suggestions if you might want to consider before you consign anything.

A link that might be useful.

www.powerhomebiz.com/starting-a-business/business-types/11-tips-when-selling-through-consignment.htm