Need help identifying trade mark and value of teapot

I have a silver teapot with the following engravings on the bottom: a rope-like design shaped like a bow, in the center of one loop of the bow is the letter “A”, in the center of the other loop is the letter “M”, below the design is the letter “S” and the words “Trade Mark”, below that are these numbers “3088” and lower still are these numbers: “64” and “4”. I googled and found an Arthur Marsh trademark that is similar. This piece is terribly tarnished, but could be silver. The handle has a section of some type of black substance, which I assume is to protect the person handling the teapot from the heat. It has a monogram on the side “ST.” I would appreciate any information you can offer about this piece and it’s origin.
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