Tin was going to be used as currency in Shattered. In a very early version of Shattered, Tin was the currency used to upgrade powers at the Black Markets, and it was earned by doing tasks such as completing missions, defeating enemies, and earning Achievements. Later on the Tin concept was scrapped and replaced with standard XP. As confirmed by Chris6d, Tin will return in Shattered 2 to replace XP, because, "Tin is more creative than XP."