Maryland Commercial Law Section 13-306
§ 13-306.
  (a)   If a gift or other inducement offered to a customer in exchange for business is not available at the time the customer complies with the conditions attached to the offer, the offeror shall:
    (1)   Give the customer a certificate which states in unequivocal language that:
      (i)   The customer has complied with the conditions which entitle him to receive the gift or other inducement; and
      (ii)   The offeror will give the customer an identical or substantially similar item of equal value on presentment of the certificate; and
    (2)   Fully comply with the terms of the certificate.
  (b)   The certificate may designate a period of not less than 90 days after the date the customer receives the certificate within which the certificate must be presented for redemption.