Is there another requirement for annual calibration of Almen gage else than digital indicator calibration and dimensional check? How to perform calibration on "calibration block"? (Specification number for calibration?)

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".