It's a 14k gold filled case. It's an anchor with serpent. I have the same watch
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Have Your Watch Case Tested to Make Sure of the Quality of Gold by: Gale
Dueber made gold cases and also gold cases which were not solid gold, that is, in many different grades. The antique gold anchor mark with no rope ( inside a shield) usually indicates solid gold, but not always.
In the Shugart book, on page 35 (the page for Solid Gold marks), there is an illustration of Dueber's 14K mark. There is a note beside the illustration that states, "This Mark means 14K Gold. Note anchor is Raised, not Engraved."
However, on pages 37-38, under, "Gold-Filled Marks", the illustrations for gold-filled Dueber marks do not show the 14K stamping - although there is a notation about the anchor being engraved for the gold-filled case stamping. At the top of page 35, there is a note that states, "Have your watch case tested to make sure of gold quality or Karat". Because the marking is confusing, and since I am working without benefit of any photographis images, I recommend the same.
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