Bulgarzoon "Whole Milk Scientifically Soured" -- claims used since May 18, 1912; "Childs Company New York NY Filed Feb 1 1915"
Link to Trademark gazette https://www.google.com/books/edition/Official_Gazette_of_the_United_States_Pa/Y5xoYPOEgScC?hl=en&gbpv=1&dq=Bulgarzoon&pg=PA343&printsec=frontcover
Child's recipe book
http://www.survivorlibrary.com/library/childs_recipes_for_cooking_and_preparing_1913.pdf
https://somersethillshistoricalsociety.org/wp-content/uploads/2020/12/WebsiteFullOctoberNewsletter2020.pdf