Thanks to Mr YS Chow - a gshock specialist for helping me with these details. Fakes are getting better, so it's best to buy from a reputable powerseller especially from eBay since eBay only allows originals to be sold on their site.

So far there are no fake PROTREK watches as these watches with triple made in Japan ABC sensors are hard to copy.

1. Ensure the box has a Marco Corporation sticker - the sole agent for Malaysia. Parallel importers or fakes will not have this sticker

2.  Original Casio watches come with either a Local warranty card or a Tourist International warranty card - depending on model purchased and if buyer is Malaysian or foreigner. Parallel importers or fakes will only offer carry in warranty only at the place of purchase.

3.  Strap buckle will have Casio Japan embossed on the reverse

4.  Back case special design engraving for each model is sharp and feels smooth. Fakes are rough and they use a sticker which you can peel off.

5.  LCD display digits are bold not slim font, sharp and straight.

6.  Watch bezel - (surrounding the watch face) will have a big G-SHOCK in white or red and in arial 0.5 font. The bezel will also be imprinted in white with SHOCK RESIST, mode, adjust, reset/split, stop/start for the various buttons.

7.  All buttons must work so you can test the light, and press the Mode to see if the screens change. 

8.  Finally the box should be printed with the following - module no, model no, water resistance rating, factory code.