When Nokia revealed the Asha 500 502 and 503 series, I didn't know what to make of its design, but it was "clear" Nokia had set a new trend with how Phones look.
The phones are double layered with the original polycarbonate protected by a clear casing.
The Asha 500 series as you already know are based soley on swipe gesture, the UI/OS is as a result or the smarterphone company Nokia acquired a while back.
The Asha series serves the prupose in the developing markets and is a dorminant force in low end sector.
It is important to note it will also belong to Microsoft once the acquisition is complete.