Part Numbering - Kemet Tantalum SMD

What does the suffix S call out on Tantalum SMD capacitors from Kemet? Why can’t I locate it anywhere?

S is no longer a valid suffix, use AH for RoHS or AT for the Lead Free (100% Matte Tin) version. The S was originally used for leaded, but was converted to lead-free with no part number change. Some customers still required lead containing products. To prevent confusion Kemet removed the S suffix altogether and changed to the other suffixes to properly differentiate the two options.