No they are not made from propane tanks.
At the beginning of my experiments i've started with propane tanks but i've tried other steel ( covex tank end from industry ) to hear the differences.
Now i'm working with some 2.5 mm thickness industrial dished ends wich i like the sound, and i make special thermic treatment to them.(and other fabrication tricks...).
With my Shiny Drums , i can play fast with hands, but with propane tanks i can't play with the same technique (fast) because it's sounds too ringy/metallic for me...