When a rent concession shall be made in the case of any lease hereafter entered into, it shall be the duty of the lessor, at the time or immediately after the lease is made, to cause such lease to bear a legend across the face and text thereof plainly legible and in letters not less than one-half inch in height consisting of the words “Concession Granted,” and to bear a memorandum on the margin or across the face of such lease stating the amount or extent and nature of each such concession, and any failure on the part of a lessor so to do shall be unlawful and a violation of this Act.