Switzerland used a hallmarking system known as "Poinçons de Maître" (Punch of the Master) to identify gold watch case manufacturers.
Yours has a "hammerhead" mark on the left with the number 161 inside:
View attachment 1404745
That mark and number identifies the case maker as Joseph Erard SA. The company is now a part
of Hermès International SA.
The mark on the right is Helvetia, the female national personification of Switzerland, and it signifies the case as 18 karat gold.
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