Jielde Lens Ring

# Background

The fresnel lens is best known for lighttowers.
However, in the 1950s and 1960s the lens was also introduced for the Jielde lamp.
It kept the dirt out of the shade and prevented to look directly into the classic light bulb during the long ours in the workshops.

The diameter of the hood varies between 159 mm and 161 mm.
The thickness of the folded edge of the hood varies between 4,5 and 4,8mm.

See also: https://github.com/martinvw/jielde-ring