Shell supported by dolphins dish

Picked this from a local thrift today. Really dismissed it as modern decor that I could make a few bucks on. Now I am not so sure. The only similar I am finding are touted as silver plate and fairly valuable.

Very heavy. It is so heavy that I thought plated iron but it is not magnetic. 4 1/2" tall. Shell is 4 3/4" x 4 2/4". Really don't think it is silver plate but doesn't seem like pewter either. Maybe something chrome plated? What do I have?

 

https://www.ebay.com/itm/166460664899 markings and better construction/quality.

Closer to yours. https://www.etsy.com/listing/1764310830/vintage-shell-dish-with-three-dolphin

 

Hadn't seen the second one. Agee it is more similar to mine. Looks like the seller doesn't know what it is either.

 

For sure not silver plate. Will polish up a bit just by rubbing. No black coming off and no silver smell.

 

Perhaps a zinc alloy?