The band playing at Mrs Windemere's party includes a guitarist playing a Gibson electric guitar (Gibson pearl-inlaid logo is visible). This is 6 years before Gibson released its first commercial electric guitar (the ES-150) in 1936. Electric guitars were an experimental novelty in 1930.
The instrument being played in the band at the party is not a cornet, but a flugelhorn. In some of the musical selections, the sound heard is that of an unmuted trumpet, in others, it is that of a trumpet with a Harmon mute. The flugelhorn, as shown has an entirely different timbre.
In the scene where Meg is painting her nails (after discovering her husband has been writing checks to Mrs. Erlynne), the nail varnish clearly has a gray plastic lid, which wouldn't have been available in this era.
The aircraft in the last scene was a De Havilland Dragon Rapide DH-89A, noted by its nose landing light and the wind powered generator on the right wing leading edge. These aircraft were built sometime after April 1934. When Mrs. Erlynne handed back the check, the date written was September 1930.