Cut Prism Plates,
The plates shell be composed of Luxfer Prism
Companies' lenses made of clear crystal, of prescription indicated
by letter or letters on the drawing and as per list and diagram attached
These lenses shall have the prisms pressed full
and extending to within not less than one-sixteenth of an inch across
the entire width of each lens.
The reverse, or plane face, shell be pressed
smooth and present a true plane; and shall be thoroughly annealed and
shall stand the polariscope test for absence of strain.
Iridian faced prism lenses shell conform
strictly to the pattern of ornamentation selected, and conform in other
respects to the requirements stated before.
The Composite and Compound Prism Plates shall
have the lenses arranged to form design pattern as indicated on the