From the Calor website:
"What is the empty weight of bottles?
All bottles will vary depending on their size, etc. The weight written on the metal disc on the shroud is the weight of the empty cylinder"
Thanks. Whats embossed on the disc is 12 00 no units. So I assume they are lbs and oz ie 5.45kg. Interestingly, the other one is 14 12 again no units but must translate to 6.7kg
Thats an astounding 23% weight difference on a standard item. Given the cost of steel , of transport for the cylinders etc I would have expected a value engineered item within a couple of percent maximum tolerance. Wouldnt you?
An easier way to tell is to get one of those magnetic indicators that attach to the side of the cylinder. Once the gas is flowing (i.e. you have to actually be using the gas), a coloured strip will indicate the level of liquid in the bottle.