This CD 155 has been underwater for years! Ocean water is slightly basic and causes the glass to take on a frosted and pitted apperance. Under magnification the surface looks much diferent than tumbled glass and frosted glass as well. There are usually traces of white powder, I think sodium bicarbonate, on the surface of true ocean glass which does not come off as a result of the rxn. The process takes about 10 years for the pollishing to start and even longer to round off sharp edges. Since insulators are chunky for the most part the pieces found are on the larger side and even mostly intact.