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This is the Simmcom SIM 800L Evaluation Board, bought November 2015 from Ebay  [ UK reseller ] for approx. 11 Euros shipped to Greece.

In order to get the documentation about the chip itself you have to register in Simmcoms M2M [manufacturer to manufacturer ] Chinese site.
Choose English from the menu on the top right of the page, click login then register. After registering and logging in head over to the product page for
SIM 800.
From there you may download the AT command manual as well as application specific documentation presenting the various functions of the unit.

The Simmcom SIM 800L EVB itself has zero documentation online (none that I could find) but is quite self explanatory. Through simple testing I was able to determine it's pin out as follows:
[table th="0"]
5V, 5 volts IN - 200mA max
GND, power supply ground
VDD, 3.3 volts  IN
SIM_TXD, serial data OUT
SIM_RXD, serial data IN
GND, serial connection ground
RST, reset [HIGH]- high impedance input

This product is mainly targeted towards the Arduino, Raspberry Pi etc
I would like to point out that scince this module has to communicate through serial to the arduino, development can be problematic as the Arduino's single native serial connection has to be connected to the PC for debug output. As such an Arduino with more than one native serial connections has to be used. Using the software_serial library is an option which has definite limitations requiring the use of lower baud rates along with the possibility for data loss during transfers.

In a followup post I will walk through the setup process, talk about the documentation and its problems on a project background featuring an Arduino.