Cristallerie St Louis Cameo Glass Vase with internal decoration

Cristallerie de St. Louis, acid carved and wheel engraved iris design, enhanced with gold. At first look, it appears dark blue over green, but I think what it happening here is that there is a dark blue layer over a crystal blue layer with an interior of yellow opalescent glass, infused with metallic inclusions, and the yellow interacts with the blue crystal layer to give a vivid green appearance. The yellow layer glows orange under black light. Marked with the acid stamped St LOUIS mark that appears to be from the 1880-1900 time period. I wonder if anyone in this group can shed light on the irregular acid stamped border that surrounds the oval mark? I think this piece is quite special. About 20 cm tall, weighs about 2.5 lbs.