Reverend Rob
Posted June 5, 2018 - 11:57am
Numbers and code inscribed in the casebacks of watches are watchmaker's marks, and they follow no set format. Each watchmaker has their own identifying system, even if you are working in a depot. Basically, each set of marks identifies a repair, or possibly a full service. The marks mean that someone has taken care of the watch, hopefully!
Mechanical watches should be fully serviced every 4-6 years, but it is rare that I see the proper number of service marks.