Ever find the pearl buttons on your clothing peeling? Well, I found a little blurb about pearl buttons in True Confessions magazine (January, 1936 issue):
To clean pearl buttons, rub with olive oil. Then apply fingernail polish and let it dry. Polish with a buffer or chamois skin.(I do hope they meant clear nail polish!)
I don't know that I'd recommend the nail lacquer unless the buttons were already peeling or near peeling... But this does seem to explain old buttons I find which seem to be flaky but when rubbed show no damage because it's just old nail polish coming off.
Related: I just posted at Collectors' Quest an article on how to select vintage jewelery -- including what repairs can be done. Also there, my Early Plastics: Identification and Care Guide.
Image of the vintage daisy necklace with blue plastic and rhinestones via my shop, We Have Your Collectibles.