Coin Metal Modification Authorization and Cost Savings Act of 2023 This bill authorizes the United States Mint to modify the metallic composition of circulating coins (including by prescribing reasonable manufacturing tolerances with respect to those coins) if a study and analysis conducted by the Mint indicates that the modification will reduce costs incurred by the taxpayers; be seamless, which means that the coins must have the same weight and diameter as current coins and that the coins work interchangeably in most coin acceptors using electromagnetic signature technology; and have as minimal an adverse impact as possible on the public and stakeholders. The Mint must notify Congress before making the modification and provide a justification for the modification. Congress may disapprove of any proposed modification through a joint resolution.