Competition closing soon!

The competition closing time is a little under 1 hr (closing end of 26 November, GMT time) away, get your answer in now! If you are still unsure of the answer here are some hints.

• Its code letter marks the spot, mark the spot with an _. Got it? too easy.
• The serial is on the '600's range and if you added up the individual numbers you would get 6. need more? ok the last digit is '0' and the second to last digit is also '0'. too easy

answers to decalcompetition@gmail.com