Thought I would add my thoughts on the C4.

The wiring was way too haphazard and untidy to have been installed with the original construction. Had to have been added after the fact, and fairly recently as in a couple of years, or maybe even less. The brick in Locke's bag looked to be in near pristine condition to have been hanging in a basement on a humid jungle island for any amount of time.

Many times batch numbers and manufacturing dates are printed on labels of all sorts, including C4.

In one of the other threads I was reminded that Sayid was in Sydney to infiltrate a terrorist cell that had C4. Would someone be able to do a screen capture on some close-ups of the C4 in their respective episodes in order to determine if the C4 could be from the same lot?