The newsstand outside of Florence's building the day after her October 25, 1944 Carnegie Hall performance has on display issues of the March 18, 1946 edition of Life Magazine (with the Eiffel Tower on the cover).
Florence tells Toscanini that her concert will be on June the 4th, Saturday night at 8pm; however the film is set in 1944, when 4th June fell on a Sunday. The previous Saturday 4th June occurred in 1938, and the next didn't happen until 1949.
When Florence Foster Jenkins is on the radio, the station also plays the Sarabande from Bach's second solo violin partita. It's played on a baroque violin, in the manner of historically informed performance. That was not mainstream until well after World War II.
The table radio in the apartment that St. Clair shares with Kathleen is a Philco model 50-922, which was introduced in late autumn, 1949 for the 1950 model year. The last radios available for sale after the Pearl Harbor attacks were introduced in the spring of 1942. Also, Kathleen turns the radio on with the right knob. On most USA-manufactured, vacuum tube table radios with two knobs (including this model), the right knob is the station selector and the left knob is used for a combination on/off switch and volume control assembly.
A few scenes in alleyways include nightclub posters. At least one refers to BeBop, which was still experimental during the war years. In 1944, Minton's Playhouse in Harlem was probably the only New York City venue where it could be heard. The word BeBop went mainstream in fall 1945.
Florence designed her costumes in real life, so surely she knows the accessories she wears with each costume. While dressing for the Valkyrie scene she asks for her amulets. St. Clair hands her the armlets that she wears during that performance and announces the correct term.
St.Clair Bayfield visits pianist Cosme McMoon in his apartment to discuss the upcoming performance at Carnegie Hall. In one shot, the back of a piece of sheet music on the piano says "The Associated Board of the Royal Schools of Music". In the next shot, the back of the sheet music is different.
Toward the end of the film, St Clair is sitting on Florence's bed, consoling her. She starts to cry, and soon tears are running down both cheeks. The camera cuts to St Clair, and when it shifts back to Florence, her face is nearly dry.
About an hour into the film, Hugh Grant (St. Clair) was out and about
in the middle of the night. In one scene, we note one of the nearby
establishments was "open", as we can clearly see by the bright,
red/blue rectangular "open" neon sign over his shoulder. Although a familiar
electric sign is commonly used today by stores and bars, flashy "open" neon signs were just
not used in the 30s, 40s and 50s.
The Carnegie Hall concert includes a mixed race audience of servicemen. While the US Armed Forces had limited integration in Europe after the Battle of the Bulge (white officers leading black enlisted men), they remained segregated until the 1950s. If white and black troops had been permitted into the facility at the same time, they wouldn't have been allowed to sit together.
The Columbia record of Lily Pons singing the "Bell Song" from "Lakmé" that is presented to Mme. Jenkins was recorded on November 30, 1944, with conductor Pietro Cimara (not Arturo Toscanini as shown in the film). This was four days after the real Florence Foster Jenkins' death, November 26, 1944.
Arturo Toscanini presents Florence Foster Jenkins with his recording of the "Bell Song" from Leo Delibes' "Lakmé" with soprano Lily Pons, on the Columbia label. Toscanini never performed with Ms. Pons; her usual conductor was her husband, André Kostelanetz. All of Toscanini's commercial recordings were for Victor (later RCA Victor) and its foreign affiliates, or for HMV, aside from two 78 RPM sides for Brunswick in 1926.
Toscanini gratefully accepts $1,000 from Florence Foster Jenkins. In real life, Toscanini would not have been short of money. In the 1940s he lived at Wave Hill, a mansion where Theodore Roosevelt and Mark Twain had lived.
Earl Wilson was not a music critic for the New York Post; he was a gossip columnist. His actual title was Saloon Editor because his usual beat was the city's nightclubs. Also, the Post is described as both a morning and afternoon paper when it was strictly an afternoon paper then. Its first edition didn't appear on newsstands until about 11:30 a.m. Finally, the copy of the Post as shown is far smaller than its actual size at the time.
St. Clair Bayfield smokes filtered cigarettes in several scenes. Marlboro created the first commercially available filtered cigarette in 1922. They were created for women, with filters to keep their fingertips from turning brown and a red butt so their lipstick would not show. Bayfield could have easily gotten filtered cigarettes in 1944.