Check the listing for details. Gould Calsurf-Certified Roughness Standard Reference Standard. Condition: Used. Listed at 199.00 USD. Gould Calsurf-Certified Roughness Standard Reference Standard Used to calibrate surface roughness guages such as the Mahr Pocket Surf. Surface roughness is a critical measurement in manufacturing to ensure parts meet specific quality requirements for performance and longevity model 21-9010-01 Vintage item from 1974 A statement of calibration is pictured. Thank you.