Product quality is graded by exterior and interior specification. 产品质量实行分等制，根据外观质量定等和内在质量评等二者结合定等。
Testing purpose also changed gradually from controlling appearance quality to an important method of insuring further processing. 测试的目的也发生了变化逐步从外观质量控制的一个重要方法，确保进一步处理。
