Lot of five 3.25x4" glass slides w/taped edges. Cardboard mounts are all marked "National Studios, Inc. of New York City." All slides advertise "RCA Radiotron" radio tubes. One slide shows boxed tube, another shows black janitor listening to radio, another shows boy tuning large imaginary radio set, another shows a boy playing trumpet in a make-believe radio studio while another shows radio repairmen at work. All feature additional image of boxed tube and "A.J. Aberndoerfer" dealer name tape strip along bottom. All are 1930s and for movie theater/school use. First slide is missing 1.75x2" corner piece of top glass slide, but piece w/image is complete. VG. Rest have some lt. aging/wear and are Fine-VF overall. Comes w/original "National Studios, Inc." postcard mailer and cardboard packaging.