This standard specifies the dimensional series and tolerances of the connecting parts of watch cases and straps. It is suitable for all civilian watch cases, and other technical watch cases can also be used for reference.
GB/T 4048-1983 history
2008GB/T 4048-2008 Timekeeping instruments.Wristwaches.Dimensions of bracelet-to-case fastening elements
1983GB/T 4048-1983 Wristwatch cases--Dimensions of fastening elements for bracelets