Halina slide viewer, c 1960.

The burgeoning popularity of 35mm colour slide photography in the late 1950s and 1960s spawned a whole new accesory industry supplying everything from slide mounts to projectors. Hand-viewers, with a simple battery-powered light and magnifying lens such as this Halina, became very popular. The slides (a square 2 x 2inches (5cm x 5cm) when mounted) were slotted into the top and the light came on when the slide was presed against a spring.