In the Activity Center there is a "Coupons" tab, they allow to buy skins with a reduced price. The only coupon I've seen at the moment is the one for Androxus Exalted Skin.
I've done some research (reddit, official forum and steam) but found nothing that explains how to get these coupons. Are they random ? from a chest ? a quest ?
How can I get more coupons ?