John Anthony Sr. became interested in jewelry while he was still in school. He learned every aspect of the trade—from manufacturing and repair to gem identification and sales. Gemstones were always his greatest passion, and he studied through the original Gemological Institute of America correspondence program.

When World War II began in 1941, John Anthony Sr. enlisted in the United States Navy and served aboard the battleship USS New Jersey. After being honorably discharged in March 1946, he opened the first John Anthony jewelry store on November 9, 1946, at 6221 Lancaster Avenue in the Overbrook section of Philadelphia, Pennsylvania.

Beyond his work as a jeweler, John Anthony Sr. was active in the Overbrook Lions Club and frequently lectured on gemstones for organizations including the Academy of Natural Sciences, the Wilmar Lapidary Museum, the Tuscarora Lapidary Society, and numerous other educational and professional groups. He also generously donated his time to the Overbrook School for the Blind.

As the business grew, it relocated in 1956 to larger quarters in Bala Cynwyd, Pennsylvania. The company was later incorporated and renamed John Anthony Jewelers, becoming one of the Main Line's most respected family-owned jewelry stores.

Throughout his career, John Anthony Sr. was a member of the Jewelers of America, the Jewelers Vigilance Committee, The Neighborhood Club, Committee of Seventy, the Main Line Chamber of Commerce, and numerous other civic and philanthropic organizations.

Even after more than fifty-five years in business, he continued working six days a week with the same enthusiasm, craftsmanship, and dedication that had inspired him from the very beginning. Spending each day doing what he loved alongside his family was one of his greatest joys and remains an enduring legacy of John Anthony Jewelers.