Affectionately known to the company as "Winchester Old" (see Opus 65 for "Winchester New,") Opus 50 at the First Congregational Church in Winchester, Massachusetts is a three-manual and pedal organ of twenty-seven stops and thirty-nine ranks. It was placed at the side of the chancel despite the objections of Charles Fisk, who favored a rear gallery location.

He therefore designed the instrument to project from the wall as much as possible to allow the organ's sound to spread into the church. Consequently, the instrument is very shallow but noticeably wide, with the Great division high in the structure, the Swell and Choir beneath it, and the Pedal divided to either side of the manual divisions.

The Great Prestant in the facade of Opus 50 is made from spotted metal, half lead and half tin, a first for Charles Fisk. Several stops of the organ were reconditioned from the preceding instrument, a much re-built Hook organ. They include the Pedal and Great Bourdons, the Stopt Diapason on the Choir, and the Great Trumpet.

Despite the concerns over the organ's placement at the side of the chancel, the acoustics of the church were very favorable to the completed instrument. In its nearly forty years of service, Opus 50 has become a recital instrument noted throughout the Boston Metropolitan area.