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]

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-freeform-solution-for-single-vision-part4 https://www.2020mag.com/article/double-asphericity-a-freefor... [1] https://www.seiko-optical.com/fileadmin/media/marketing_shop/order_artwork/SEIKO_Endconsumer_Flyer_AZ_en_ok.pdf https://www.seiko-optical.com/fileadmin/media/marketing_shop...