Hello Zach
give us an educated guess - what wud you say is the height of the white image above the blue - less than half a mill., more than a mill. Cameo, in its simplest
form, is an image in relief after cutting away surrounding glass - in this instance cutting away the blue to leave white.
Another line of thought might be - if the white had been cut to blue, wud iridescence remain on the blue (right up to the white). Best of Luck with your search. cheers Paul S.