Bought it at 30 Aug 2015. As a gift to friend but wrong serial. Just sell it for 7000 RMB.(7988 on Apple.com) Guarantee period to 29 Aug 2016（you can call Apple Hotline).
iMac Summary:
21.5-inch (diagonal) LED-backlit display;
1920 by 1080 pixels;
1.4GHz dual-core, Intel Core i5;
500GB or 1TB 5400-rpm hard drive;
Intel HD Graphics 5000
Other Features
Four USB 3 ports
Two Thunderbolt ports
802.11ac Wi‑Fi
Bluetooth 4.0 wireless technology
Gigabit Ethernet
FaceTime HD camera
Apple Wireless Keyboard
Magic Mouse or Magic Trackpad
SDXC card slot
OS X Yosemite
Photos, iMovie, GarageBand, Pages, Numbers, Keynote