[1][2] The 1910 federal census documents that the Coolidge household included two live-in maids and a full-time cook, indications that Sydney's executive positions and income provided his family with an upper-class lifestyle.

[3] By 1938 he began acting regularly in New York City, where that year he was cast as the church organist Simon Stimson in the original Broadway production of Thornton Wilder's play Our Town, which was presented at Henry Miller's Theatre and co-starred Frank Craven and Martha Scott.

[5] His final appearances on the "Great White Way" were in the early 1960s as Mr. Nicklebush in Rhinoceros and as the Danish ambassador Voltemand in a modern, highly stylized interpretation of Hamlet directed by John Gielgud and starring Richard Burton.

The popular trade paper Variety in its January 17, 1951 assessment of Darkness at Noon commends the actor for his "persuasive" representation of a "sardonic political prisoner" trying to survive the brutality and paranoia of a Soviet-style revolution.

[7] The following year, in its October 15 review of The Gambler, the critic for Variety includes Coolidge among what he describes as the play's "unusually good" supporting cast, more specifically for the actor's portrayal of Commissioner Costa, "the practical but puzzled trial examiner".

[3] The veteran actor had continued to perform until shortly before his death, managing to complete the filming of his scenes as the character "Fingers" Felton in the Walt Disney production Never a Dull Moment.