English Vintage Silver Watches Age Determination by Case Hallmarks from 1544
British hallmarks on the case are another method of determining age.
For each quarter of a calendar year, a letter in a specific spelling was defined in London from 1544. Using the lists below, one can determine the silver test (usually a few weeks after completion) of an English silver pocket watch not only exactly to the year, but even to the quarter of the presumed year of production.
These markings are required by law for cases made of precious metals such as silver or gold. Precious metals are not typically used in their purest form. They are often alloyed with other metals to improve their durability and workability.
Hallmarks are symbols applied to precious metals to indicate the purity of the alloy.
London Hallmarks
Source: silvermakersmarks.co.uk, timewornwatches.co.uk