I hate to say this, but are you sure it is ivory? I have seen some plastics do this but never ivory. Not "little yellow blisters". Ivory coming loose in the middle of the piece will form a large blister. Have you spoken to the customer about this? It may well have been that way before being stored. Check the material with a knife blade edge by gently scraping along the side of the tail. If it is ivory the blade will slide along with no resistance. If it is any form of plastic the knife edge will dig into the material and not move at all easily. Don't bear done too hard or you can damage the plastic. Newton
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