It's quite an elegant design, and obviously a fair amount of work in Mercerized Crochet Cotton. But, what a beauty!.
I've searched Google-land and can't find anything that matches to this pattern. The pattern is PC 1021. Now, I've seen this prefix series many times (PC), and it's typically a designation for 1940's/1950's from Spool Cotton Company. On many occasions, SPC allowed the National Needlecraft Bureau to market their patterns as well. Since this is obviously a mail ordered pattern, I'd assume it would be National Needlecraft.
Of particular fun is the caption of unknown writer -- "Isn't this a pretty dress. I'd love to have one like this. Wished I could crochet".
Hope you enjoy the vintage advertisement. Thanks for dropping by.