Mid-century vintage Holophane studio task lighting diffuser lens

Retro mid-century, square Holophane prismatic glass light diffuser lens. This vintage task light diffuser is marked Holophane and two patent number from the 1950s on the bottom edge of the shade. The first patent is a design patent from 1952 (this patent covers the specific shape and design of the lens and the patent references patents from Luminare and products from Moe Brothers). The second patent is a regular concept patent from 1957 demonstrating the use of this diffuser lens with industrial or studio work task lighting. We've included a photo of the task lighting patent below.

Both US patents list the inventor as Kurt Franck (one of the main designers for Holophane).

This square Holophane diffuser measures about 12" square, 1" high and the glass is about 0.30" thick. The concave side of the lens has a bulls eye fresnel lens pattern for diffusing the light and is marked "This side away from lamp".

This light shade is in excellent condition with no chips or cracks.