This is the new router RT-N13U from ASUS, as I can understand, successor of Wl520g series.
Here the additional specs:
CPU: Ralink RT3052F 384Mhz (MIPS 24K)
RAM: 32Mb (2 x 16Mb)
ROM: 4Mb
USB: 1
WLAN: Dual Radio N
OS: Linux version 2.6.21
Bootloader is U-boot, serial console (see pinout on second picture) has 57600 baudrate.
Internal photos: