Images said reveal an upcoming Nokia Lumia smartphone appeared on the popular Chinese social network Sina Weibo earlier this week. The images, which have been confirmed as authentic by WPCentral, show an improved design with an aluminum case, a shift away from the traditional polycarbonate cases of past Lumias. The upcoming handset is said to be equipped with a 4.5-inch display, a dual-core 1.5GHz Snapdragon S4 processor and an 8.7-megapixel rear camera. Other specs are rumored to include 16GB of internal storage, 1GB of RAM and a 2,000 mAh battery. The smartphone will reportedly be announced on May 15th for a late June release date on T-Mobile. A second image follows below.