Limited Edition/ collaboration models you can only get it in G-Factory outlets.
Think twice about getting from these resellers... warranty is an issue in case anything goes wrong with your watch.
Grey source meaning the watches don't come through the authorised distributor. It came in "through other sources" where it's unknown.

There's no telling whether it's "safe"or not. You could have bought fakes without realizing sometimes. In fact, warranty is also an issue. While GS is known to be tough and durable, there have been cases or people being unlucky to have one that malfunctions after awhile. When you get it from authorized source, there's no worry about warranty. If you get your watch fixed elsewhere, be careful about it. G-SHOCK is water resistant and there are some ways that the technicians open and secure the watch lock and screws. Outside watch repair may not know, and friends have told me water entered their watch after it's fixed outside.

Give yourself the peace of mind and get from authorized source. IMO the price difference is not so huge to the point I'll take the risk, personally speaking.

This is not official from Marco or Casio Malaysia. Beware.

gfactory rm1509 retail.