Martha Stewart collects old yellow ware, along with lots of other folks. I think many collectors use the low pie plates for their place settings. Although yellow ware has been produced since the 1600s, dinnerware plates and sets made from these yellow clays where not generally made until the mid 1800s when they were mass produced with the use of a "Jigger". Jiggering is a method of making pottery by pressing a ball of clay into a plaster form on a potters wheel. This doesn't take much skill and was a form of mass producing pottery. Plates made by jiggering were made with flat rims like the plates you buy everywhere today. However, the flat rims tend to warp and fall while being fired in the kiln. Large potteries used rolls of clay between plates to support the rims during firing.
Before the large factories took over the small potteries in the 1800s, plates were not made by small potteries because of the warping and complications in firing.
My plates have slightly raised and rounded rims, with a rolled edge. This keeps them from warping and mades them a little more durable. Hand thrown pottery plates are a little heavier than the pressed plates but they have their own charm. Visit my web site for more information on dinner ware. www.eastknollpottery.com