apparatus for manufacturing a hydrogen 21 line precision measuring device , comprising : a hydrogen 21 line generator , which may be a hydrogen maser , which generates an emission spectrum comprising a spectral line at substantially 1420 . 40575177 mhz and communicates the spectral line to a frequency counter ; which is adapted to receive the spectral line , measures frequency of the spectral line , and communicates an indication of the measured frequency to a computer , which receives the indicated frequency , calculates wavelength of the indicated frequency and communicates control signals to a laser or other marking device to scribe markings on a measuring device substrate at one or more intervals of the calculated wavelength and subdivisions thereof , resulting in the measuring device substrate having a plurality of scribed markings , each pair of the scribed markings at an interval of substantially the calculated wavelength and each of the subdivisions thereof equaling a portion of the calculated wavelength .