Fluid relative density measured against water with both materials at 60 degrees F and reference pressure of 14.696 psia (or equilibrium pressure). Equivalent to "RD 60/60"
EESiFlo North America, Terminology and Glossary: Maritime Terms, Pennsylvania, USA 2002, flowmeterdirectory.com/flowmeter_terminology. (Mrtm/ Ports and Ships - Amer) {539}