Broadway Across America's touring production of Wicked successfully used its props to help convey a sense of time, place, and character in the show. Since this was staged as essentially a bare-stage play, the props were an important aspect of the scenery.
In the middle of the musical number "Popular," Glinda whips out a hand-mirror for Elphaba to examine her new look. This hand-mirror was also a throw-back to the late 30's/early 40's. Glinda's use of it in this scene reflected not only the time period of the show, but also the self-centered nature of Glinda's character at that point in the story.
Later in the play, Elphaba's selfish and pitiable sister admires herself in a similar hand-mirror. This character, Nessarose, has gone from young, out-going, hopeful, and naive, to old, crotchety, and self-absorbed. She's reminiscent of the evil witch in Snow White. It's almost as if Nessarose could be saying "Mirror, mirror [in my hand], who's the fairest [in the land]?" as she strokes her shiny black hair while looking in her mirror. Her obsession with her hand-mirror helps to show the negative change into wicked witch status of her character.
Near the end of the play, Glinda has been changed, for good. She's gone from the all-about-me-girl, gazing in a hand-mirror, to looking out beyond herself. This is seen in her use of the 40's era microphone. At first she is showing-off, announcing her "surprise" engagement at this stand microphone. She's taking advantage of the latest technology to keep herself center-stage (literally and figuratively). Later, though, she uses that microphone to honestly and openly communicate with the citizens of Oz.