[goldenkey]

Seiko's US website has some PDFs if you do some searching but the JP website is a far better resource, and the products are international for the most part. [1]

You can read about the double aspherics here:

https://www.2020mag.com/article/double-asphericity-a-freefor...

[1] https://www.seiko-optical.com/fileadmin/media/marketing_shop...