When you are researching a time period or dressing a set, remember that people do not buy all new things every single year. A real house or apartment is filled with the clutter of the entire life of the people who live there. My parents, for instance, do not have a house decorated completely from items taken out of this year’s catalogs. Their furniture ranges in period from contemporary all the way back to Victorian. So a play about a similar English couple living in the Victorian period could have furniture ranging from Victorian back to Regency, or even Georgian.
When you study different period styles, you often run across lists and descriptions of what was “popular” or “in style” during certain time periods. Another idea to keep in mind is that most people are very varied in their stylishness. Some people always seem to be up with the latest trends; others have excruciatingly bad taste. During the Art Deco period, Ancient Egyptian motifs and styles came into vogue. That does not mean that someone would have thrown out all their furniture and decorated their place entirely in Egyptian-inspired furniture. Depending on how important style is to your character, there may be a few such pieces scattered throughout; there may also be none. Many of the characters in plays cannot afford to buy new furniture whenever tastes change.
Finally, I wanted to point out something which is obvious to many prop masters but not often to beginners. If your play is set in the 1920s, and you find a number of antiques from the 1920s, they will have a natural aura of age. Metal will have rust and patina, paper will be yellow and brittle, paint will be faded and peeled. This is not what the items will look like in the world of the play though. If a play is set a hundred years ago, that does not mean the items will look a hundred years old. Quite the contrary, the items will look new and well taken care of. A book will have bright white pages, metal will gleam and paint will be fresh. Obviously, the play itself can have antiques or old items; my point is that the contemporary props in a period play need to appear contemporary. For many props, you cannot use any but the most well-preserved antiques; you will have to find modern substitutes or construct your own.
“…contemporary props in a period play need to appear contemporary”
Under normal circumstances, I would absolutely agree with you (assuming that the design of the show isn’t based upon some sort of stylized concept), but I’ve found that there is “reality” and then there’s “stage reality,” which is heavily influenced by audience expectations. Something I discovered when I did a prop design for a period show with props that I fabricated and refurbished to appear contemporary to that period. The problem I noticed after the fact was that the audience had been so used to those objects appearing as antiques (with all of the implications of age and wear that goes with it) in the normal course of their lives that seeing them out of that context became somewhat distracting. It’s rather akin to the dull, loud pop of an actual gunshot sounding just plain weird to an audience that is accustomed to hearing the heavily processed and artificial sound of gunfire in films and television. It’s an odd situation, where the interpretation of reality for the sake of an audience’s experience based upon their expectations clashes directly with the aspects of actual reality.