There are no "industry" specifications calling for Almen gauge calibration frequency. In these cases the manufacturer's guidelines are used and this would generally be annually unless conditions suggest re-calibration would be appropriate. The "Check Block" (it is NOT a calibration block) requires flatness check on the one side. The other side, the curved side, is not calibrated and does not need to be re-calibrated. Calibration of a curved surface like this is very expensive (over $10,000 from NIST)and therefore it is declared to be a "Check Block", not a "Calibration Block".
