GB/T 43550.2-2023一般用途活动铅笔和铅芯分类、尺寸、质量和试验方法第2部分:黑铅芯国家标准
英文:Mechanical pencils and leads for general use—Classification, dimensions, quality and test methods—Part 2: Black leads...
英文:Mechanical pencils and leads for general use—Classification, dimensions, quality and test methods—Part 2: Black leads...