This entry records a numbering problem rather than a separate standard. In the Chinese system the prefix GB denotes a compulsory national standard and GB/T a recommended one, and the same technical document has been carried under both designations as the requirement moved from a compulsory to a voluntary basis. Purchase specifications, type test reports and manufacturer declarations circulating in China still quote the compulsory number, while current approvals and the catalogue of the national standards body use the recommended number, so the two appear side by side in project documents for the same device. For a supplier entering the Chinese market the practical consequence is that the number to be cited in a test report must be confirmed with the customer's technical department rather than taken from an older specification, since a report quoting the withdrawn designation may be rejected at the approval stage even though the tests performed were equivalent.