ATHENA MSFC XRCF and Goddard Space Flight Center Science Team successfully conducted an Engineering Peer Review (EPR) 6/8-9/22. The EPR scope was to assess the current metrology approach and design of the Mirror Assembly Module Demonstrator (MAMD) Phase III testing. The EPR Panel consisted of Subject Matter Experts within NASA, industry and academia. Presentations included overviews of the XRCF facility and historical approaches for mirror calibration, as well as preliminary Calibration Planning for ATHENA and proposed Metrology tools and approaches. Recommendations from the EPR Panel Members are anticipated 6/24/22.