Victorian blue polka dot pattern satin glass vase

I got this pretty Victorian vase at the monthly antiques fair last weekend.
It is made from three layers of cased glass - clear over blue with a polka dot air trap pattern, & a white interior. The vase measures 10 cm tall, 5 cm across the top rim, & 5.5 cm across the base.
There is a small clear crest on the slightly crimped top, & a rough pontil mark on the base.
Possibly an example of Riedel's Atlas glass.