I have several sets of "weighted sterling" salt & pepper shakers. One set has the glass inserts.

In weighted sterling, the metal is sterling, but thin. It is formed over other material, such as plaster. The bottoms will have concentric circles, the words "weighted sterling", and usually a number ( 3 or 4 digit) that is the catalog number.

And I agree that Replacements Limited is a great place to find out about patterns. Good call, CarolC.