The classification boundary turns on whether the glass has been subjected to optical-quality grinding, polishing, or figuring to achieve specific optical performance parameters. A rough-pressed or sawn glass blank that has not been finished to optical tolerances remains 'not optically worked' and belongs here. Once the element is ground and polished to a specified surface figure or transmitted wavefront quality, it crosses into the worked optical elements heading. Manufacturer process documentation and inspection certificates help establish which stage the imported article represents.

Traffic and railway signal lenses used in US infrastructure projects are often subject to ANSI/ITE or AREMA specifications governing colorimetric performance, luminous transmittance, and thermal shock resistance. Importers supplying public-sector transportation projects should confirm that their products meet the applicable American National Standard or project specification, as non-conforming signal glass can be rejected at the project level regardless of customs clearance status.