I have this unusual insulator but can't find any info online about it. The lighter pic was taken using a flash to show more of the interior detail. It has "seams" down the outside but not inside, as though it was molded. The golden discolorations look like oxidation but the item is not that heavy (weighs a little over 10 oz.) and not metal. It sounds like wood when you knock on it but I can't see any grain. Any ideas?