a photo of the entire set

The base material is copper. I believe you have silver plating, not silver cladding. The plating can vary from very thin to substantial. A thin plate may be .0005 to .001 inch thick. Electroplating can apply thicker coatings, say up to ,005 in thk. It depends on how much cost the maker puts into the product and his selling price target.

I am not familiar with the marks on your piece, but do not see any indication of plating thickness. Be very careful with cleaning plated silver as it is easy to rub through the coating. Electroplate tends to be thickest on edges, corners, and points and thinnest on flat surfaces.

Birmingham Silver Co in Yalesville Ct. They were the successor to a company founded in 1932 which became Birmingham Silver Co some time pre-1957, so your set likely dates from after that time.

Here is a link that might be useful: Silverplate marks

what is its worth

Compare on eBay. Whatever someone will pay, which often isn't much these days as old formal serving ware isn't terribly popular any more.

I have a set that was my Aunts. I don't serve Tea, so I use them as vases for cut flowers. This way I use them and think of my Aunt.