CO2 Cylinder 2 kg, Slightly Used

Refillable CO2 cylinder, very slightly used (nearly full).  According to my measurements the total mass of cylinder, turn valve and remaining CO2 is 6.9 kg, which is still higher than the nominal "full" mass of 6.2 kg. So as I understand, it is nearly full.  See photos.

Reason for selling: I bought the CO2 to use for preserving certain types of paint in partly-used tins.  It does not seem to work well for this application and I have no other use for it.

I bought this from an online store that supplies craft beer producers.  I paid R1195 for the cylinder with 2 kg CO2 inside. Now it seems to cost R1380 empty.