Notwithstanding the provisions of section 22 hereof [15 USC 1072], a registrant of a mark registered in the Patent Office, may give notice that his mark is registered by displaying with the mark the words "Registered in U. S. Patent and Trademark Office" or "Reg. U.S. Pat. & Tm. Off." or the letter R enclosed within a circle, thus (R); and in any suit for infringement under this Act by such a registrant failing to give such notice of registration, no profits and no damages shall be recovered under the provisions of this Act unless the defendant had actual notice of the registration.