The yellow cylinder which was found on a balcony of a Douma apartment shows grid marks which are of the same size of the remains of a fence which was found next to the cylinder. This is another strong indication the yellow cylinder filled with chlorine was dropped by a Syrian air force helicopter over Douma at April 7.
The grid marks became visible only after the OPCW visited the apartment. Possibly the investigators of OPCW moved the cylinder and turned it around. Previously made photos of the cylinder while in its original position did not show the grid marks.
The grid marks on the side of the cylinder which hit a horizontal positioned fence is another strong indication a helicopter dropped the cylinder.
The fence (wired grid) was possibly used as a shade or to be used as a drying rack. The frontside of the building shows similar shades on top of the balcony.
Other indications of a helicopter dropped cylinder are the damage of the house, the axis and wheel and the remains of the harness of the cylinder.
The photo below shows the grid marks.
Michael Kobs, a German national doing investigations on Syria related events, made the composition shown below. It shows the various sides of the cylinder. The compostion makes clear only a certain side of the cyliner has a grid shaped damage. The composition also makes clear the soot is not equally divided over the cylinder, which makes sense.
The grid marks are seen on the side with the most black soot. Another indication this side was the side touching the concrete. Most left the grid marks, most right shows the upper side of the cylinder in its intial position.
Another indication of a dropped cylinder is the corner of the building above the balcony which appears to be missing some concrete. It could be the cylinder hit this corner.
Another indication of a helicopter dropped cylinder is this axis with a wheel attached to it. Some of the cylinders dropped by Syrian air force have a steel harness with axis and wheels to make it easy to push the cylinder out of the helicopter.
Another indication is the piece of metal indicated by the red box in the picture below. It looks like a part of the harness of the cylinder.