An unannounced Samsung SM-G7102 found its way to the FCC for testing and its user agent profile is up on Samsung's site. The G7102 is an Android 4.3 Jelly Bean smartphone with a 5.25" 720p screen.
Despite the relatively low pixel density of the screen (288ppi), the processor clockspeed is listed as 2.3GHz, which can only be a quad-core Snapdragon 800 chipset. It's a fairly large device, measuring 147 x 75.1mm.
The FCC docs don't come out and say it, but Samsung SM-G7102 appears to be a dual-SIM device. This means it will probably launch in East Asia first, perhaps as a low-cost alternative to the dual-SIM Galaxy Note 3.

SOURCE

I've heard about this model, however, its seems that there are not images available online to let people know how it looks like.

I guess that common people have to wait until the official release is announced, because at the end of the day the product have to be available in stores before people can buy it.

One more question... how the clock-speed affects the overall performance of the phone?

Regards