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		                        | National Stock Number:
 1240-01-497-4320
 
 Federal Supply Class:
 1240
 
 National Item Identification Number:
 014974320
 
 Description:
 WINDOW,OPTICAL INSTRUMENT
 
 Detail:
 A COLOR FREE ITEM OF TRANSPARENT OR TRANSLUCENT MATERIAL, USUALLY OPTICAL GLASS, HAVING SPECIFIC LIGHT DISPERSIVE AND REFRACTIVE PROPERTIES. THIS ITEM MUST HAVE TWO PLANE-PARALLEL SURFACES AND IS DESIGNED FOR USE IN AN OPTICAL INSTRUMENT TO PROVIDE A BARRIER TO FOREIGN MATTER AND/OR PERMIT LIGHT TRANSMISSION IN OR TO THE OPTICAL SYSTEM.
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 Manufacturer Information:
 
 | 5612975 | 53711 | NAVAL SEA SYSTEMS COMMAND | 
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 Techincal Specification:
 
 | DIAMETER | 41.9 MILLIMETERS MINIMUM AND 42.0 MILLIMETERS MAXIMUM |  | MATERIAL | MAGNESIUM FLUORIDE  AND GLASS OPTICAL LOCATION NOT OTHERWISE SPECIFIED |  | PART NAME ASSIGNED BY CONTROLLING AGENCY | EYEPIECE,EL-1 |  | POLISHED PERIPHERY | NOT PROVIDED |  | SPECIAL FEATURES | CONVEX RADIUS IS 55.4 MM MAX |  | THICKNESS | 8.9 MILLIMETERS MINIMUM AND 9.0 MILLIMETERS MAXIMUM | 
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