Kopp Glass lenses 2 in a 6 3/4 3 3/4 

Company Name: The words "Kopp Glass" are frequently embossed along the outer edge.Part Numbers: Look for codes such as TL (Traffic Lens) followed by a 4-digit number, like TL-4666.Optical Specs: Markings often include the diameter and focal distance, such as 6 3/4 D followed by a focus measurement (e.g., 3.125 F).A.A.R. Testing: Some vintage railroad-specific lenses will be marked "A.A.R. Tested," indicating they met the American Association of Railroads' strict safety standards.Common Applications for 6 3/4" LensesTraffic Signals: Before 8-inch and 12-inch lenses became standard, these 6 3/4" and 6 3/8" lenses were used in early traffic light units.Aviation/Airfield Lighting: Kopp's aviation-grade glass is used for approach and beacon lighting.Marine & Industrial Signals: These heavy-duty Fresnel lenses were common on large nautical signals and tall industrial "danger" beacons.

selling as pictured.

more than welcome to pick up at shop in butler pa & save shipping.