 The American Bayer, owned by Sterling, retained the rights to use the "Bayer" brand for selling aspirin in the US, the UK and the Commonwealth.In 1923 Sterling purchased a 25% interest in The Centaur Company, manufacturer of Charles Henry Fletcher's, Fletcher's Castoria.In 1940, a cross-contamination from equipment sharing resulted in Winthrop Chemical producing contaminated sulfathiazole tablets contaminated with phenobarbital.