After changing hands many times and still regarded as the finest drugstore in New England, the Caswell name was still considered synonymous with medicines and chemicals under the Caswell, Massey & Co., Dispensing Chemists name.

In the early 1880's, the company was operated by John R. Caswell, William M. Massey, and Lyman B. Blackman. They were located in New York City at 1121 Broadway at the corner of 25th Street, and also at 578 Fifth Avenue at the corner of 47th Street. The company was also still in business in Newport, RI at 167 Thames Street at the corner of Mill Street, and also at the casino Building on Bellevue Avenue near Ocean House.

Throughout this period they were corresponding with chemists in London at Curtis & Co., and with chemists in Paris at W. H. Swan.

Caswell, Massey & Co. became the sole manufacturers of the New Aperient, Effervescent Grape Saline which was prepared from ripe fruit. This product was a "... beneficial remedy for indigestion as well as a preventative for infectious diseases, good for gout, rheumatism, blood poisoning, and very effective as a laxative."

By 1906, Caswell, Massey & Co. were succeeded by the Hall & Lyons Co., N. E. Apothecaries, located at 212 Thames Street in Newport. Hall & Lyons ran the business until 1915.