The South Carolina Department of Revenue, with funds already appropriated to the department, shall print and distribute to each business establishment in this State, to which has been issued a retail sales tax license, a cardboard placard not less than eight inches by eleven inches which shall bear the following inscription in letters not less than three-fourths inch high:

"BY ACT OF THE SOUTH CAROLINA GENERAL ASSEMBLY ANY PERSON CONVICTED OF ARMED ROBBERY SHALL SERVE A SENTENCE OF NO LESS THAN SEVEN YEARS AT HARD LABOR WITHOUT PAROLE."

Such placard shall be prominently displayed in all retail establishments to which they are issued.