- The details that confirm the S/N range 18000 - 22100: The stop works barrel identify it to be AT& Co. grade, and post 18000 (certainly >17000). The arm on the SU balance (wider at the rim with a hole) is pre 1860. The first series click is pre 28000. The cantilevered potance is post 15000 (can't be a DHD movement). The toe end escape wheel started around 16000. Sprung under hairspring is pre 25000.
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