On 3 August 1961, Federal Specification GGG-P-463B was issued to provide requirements in United States customary units for igneous rock (granite) surface plates for use in precision locating layout, and inspection work. It encompassed new certification, recertification in the field, and recertification after resurfacing. GGG-P-463B was later revised and reissued on 12 September 1973 as GGG-P-463C, which provided common language and terms of classification for surface plate manufacturing and commerce. On 15 June 1977 an amendment was issued to the federal specification in order to include requirements in metric units.