This is an L-plan, shallow gable-roofed, two-story frame structure on a raised, brick basement. A brick boiler house adjoins the building to the rear. The front (east-west) component of the L plan is 70' long and 35' wide. Extending perpendicular to this block and housing the main manufacturing area is a north-south wing that measures 115' by 30'. An original front pavilion measuring 20' in width and 15' deep provided two stories of office space with a front entrance. A 3-story brick tower originally supported a wooden water tank. This tank was removed before 1939. Original frame windows were double-hung, ⁶⁄₆ with a 3-light transom. After 1964 these were replaced with the current aluminum, horizontal-light, industrial windows. The interior manufacturing space is clear span, with a slow burning, plank-on-beam floor. King post roof trusses are timber with steel tie rods. A rear, attached boiler room comprises a tall, single-story chamber with an attached 90'-high, brick, round-section chimney. This mill was built ca. 1905 to replace a complex of frame structures that had evolved since the original Sadler and Stanley operation began in 1863. The Sadler Brothers factory, converting to a mix of jewelry and optical products manufacture in the mid-1920s, remained in operation solely as a manufacturer of optical products and owned by the Sadler family until 2009.

In 1863 George W. Sadler (1831-1884) and Daniel O. Stanley purchased several acres of property in South Attleboro and began the manufacture of women’s hat and dress ornaments. When Stanley left the partnership four years later,43 Sadler, a native of Mansfield, MA, became the sole owner of the business. His original purchase with Sadler had included a Greek Revival residence belonging to George Draper of the tannery family (553 Newport Avenue, q.v.). Over the next thirty years Sadler and his successors erected on this property a complex of frame, generally single-story factory buildings powered by a steam plant. In 1869, when brother Albert D. Sadler joined the company, it was renamed Sadler Brothers, a name that would continue for the next 140 years. Upon Albert’s death in 1873, the company reverted to the sole ownership of founder George W. Sadler. When he died in 1884, the company came under the direction of his 24-year-old son Herbert W. Sadler, Sr. (1860-1931). At that time the company employed fifteen operatives and had supplemented its product line to include the manufacture of gold-plated bracelets. Five years later, Herbert brought his younger brother Thomas G. Sadler, Sr. (1871-1947), who had apprenticed under him, into the firm as partner. The company expanded dramatically in the period from 1890 to 1910. The original mill complex was demolished in 1905, its multiple frame buildings consolidated into the two-story, L-plan factory building (with attached brick boiler house in the rear) that survives at 561 Newport Avenue. Construction of the new Sadler factory occurred simultaneously with the development of company-built housing along Newport Avenue and Park Place. Four company-built double houses front on Newport Avenue in the immediate vicinity of the factory. These include the Queen Anne houses at 550-552, 556-558, 569-571 and 579-581 Newport Avenue. At this time the company also erected a modest, 1½-story frame building directly in front of the mill which, over the next century, would serve as a garage and (when relocated west of the mill on Park Place in 1911) as a Community Hall for Sadler employees. By 1909, the company laid out a private way to the immediate west of the factory (Park Place) for the construction of four Queen Anne-style cottages. These survive at 16, 20, 26 and 27 Park Place. Reflecting the company’s early 20th-century prosperity, Herbert A. Sadler built the Colonial Revival mansion at 574 Newport Avenue in 1906. Designed by Samuel Fuller of Pawtucket, this house was individually listed in the National Register of Historic Places in 1982. As noted in the nomination, “the house, which remains one of the most prominent pieces of architecture in South Attleboro, served as an impressive as well as convenient place for receiving and entertaining the firm’s clientele.” Herbert A. Sadler retired from the company in 1926 and died in 1931. His wife Grace remained in the mansion until her death in 1951. A few years later the estate was sold and converted for use as an elderly rest home. It is now the Victorian Mansion, an assisted living facility.

In 1926, Thomas G. Sadler, bought his father’s interest in the enterprise, converting it for primary manufacture of optical findings and tools. Business directories of the period indicate that the production of celluloid and other novelties continued for some time as a secondary product line. He incorporated the business in 1928 as Sadler Brothers Optical Tools and Findings, by this time employing about 50 operatives. Thomas G. Sadler, Sr. died in 1947. Two years later, his son, Thomas G. Sadler, Jr. (1895-1977),44 assumed ownership of the company. Between 1935 and 1962 he sought and received five U.S. patents. Although the first of these was for a generic type of lid latch, the remaining four were inventions of or improvements to optical devices. The company exploited these patents, expanding through the post-WWII years to a staff of sixty and continuing in operation as a family-owned business until its closing in 2009.