"The Family Christmas Tree" - View Lights.

I have a set of 10 Ornament Photo Slide View Lights made by Cargile Co, View Light Products Mfg. 25, Stanley St. 1/F., Central, Hong Kong.
U.S.A. Patent No. 3.694.648. They are still in their original box and have never been used. The way these lights work is you take a slide from a 35mm picture and place it in the slot on the light and it is lit up and magnified as a picture. Does anyone know the approx. age and value of these lights? I have had them for 25+ years.