It seems like you are referring to a specific steel grade called A400-69 (2012). Unfortunately, without more information, it is difficult to provide comprehensive details about its chemical composition, mechanical properties, and standard number.
A400-69 (2012) is likely a designation specific to a certain industry or organization, and it may not be widely recognized outside of that context. To obtain more detailed information about this steel grade, it would be necessary to consult technical specifications or reference materials from the relevant industry or organization. These documents should outline the chemical composition, mechanical properties, and specific standard number associated with A400-69 (2012).