Ground and Polished Glass
Alternative term: Cut Glass
Glass formed, after solidification, into the shape required for optical purposes by cutting roughly to shape initially and subsequently shaping accurately by grinding and polishing, using abrasive powders at first coarse and becoming successively finer.
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM