FMC 1278 uses the older designator of the American manufacturer, in which the letters identify the company rather than the class of the document, and it belongs to the generation of requirements that preceded the present specification system. Documents of this age survive because drawings, tooling approvals and long-running supplier agreements continue to cite them, and a supplier who meets one should establish whether it is still maintained or whether it has been superseded by a specification in the manufacturer's current system. Where it has been superseded, the practical questions are whether the levels have changed and whether the test methods now called up differ from those originally used, since a report produced years ago against an older method may not be accepted as evidence against the current one even if the level is unchanged.