This is a set of green Depression Glass mixing bowls. They weren't found as a set, I've been collecting them as I find them in antique stores or flea markets or auctions. I've managed to find four of different graduated sizes, all the same shade of green with the same ribbing.
Depression Glass was manufactured in the 1930s. You can find Depression Glass bowls, dinner plates, candlestick holders, glasses, teacups, sugar bowls, sherbet dishes, water pitchers and more. The most common colours are green, clear, and pink. Depression Glass also comes in yellow and blue. There are different shades of green, one is sort of lime, the other the green you see in this photo. There are many different patterns too. Depression glass is eagerly sought after by collectors and can be quite expensive