This International Standard specifies a series of values for the magnification of imaging components of light microscopes and defines a number of magnifying systems to which they apply.
BS 7012-1:1998 history
2015BS ISO 8039:2014 Microscopes. Values, tolerances and symbols for magnification
2012BS ISO 8039:2012 Microscopes. Values, tolerances and symbols for magnification
1998BS 7012-1:1998 Light microscopes - Specification for the magnifying power of microscope imaging components