In the early 1900's many Americans experienced new wealth. They displayed their wealth by having elaborate table settings. A set of china may be glass, porcelein, or pottery. Many extra pieces were used at the table.
One of those was the mayonnaise. Picture yourself planning for a big social dinner in 1920. You have plates and silver. What do you do with something like mayonnaise? You can't just set a jar on the table! Instead, you have a three-piece glass set. A small plate with a bowl on top filled with mayonnaise and a scoop/label ready to scoop up the mayo.
You can find mayos made in Depression era glass and in porcelein. I started this collection because I like glass, but I don't want a complete dinner set for each piece I like. At an antique show in Nacogdoches, I found a pink glass mayonnaise in a style that was called elegant depression. Since then I have picked up mayonnaise sets on ebay and at various shops and shows. For today's table they are great for dips as well as mayonnaise.