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It was used on a grade of Hampden starting in the 1890s.
"I can confidently tell you that the anchor was used on movements and dials many years before the trademark in 1905".
Generally, the trademark documentation includes details regarding how long the mark was used prior to the application.it is also possible/probable the 'Anchor in Shield' mark appears on Dueber watchcases also before the 1873 trademark was filed --- and possibly back to the early 1864 year of the fledgling Dueber watchcase operations.