A method for determining a test strip calibration code for use in a meter includes inserting a test strip into the meter. The inserted test strip having a substrate with a working surface for receiving the body fluid sample and a reverse surface that is in opposition to the working surface. The test strip also includes a permutative grey scale calibration pattern disposed on either of the working and reverse surfaces, with the permutative grey scale calibration pattern including more than one grey scale region. Moreover, the scale regions of the test strip define a grey scale permutation that uniquely corresponds to a calibration code of the test strip. The method also includes detecting the permutative grey scale calibration pattern with a grey scale photodetector module of the meter and determining a calibration code that uniquely corresponds to a grey scale permutation defined by the permutative grey scale calibration pattern based on permutation matrix stored in the meter.