I made a diffuser plate for my GOSM, ...while I was at the store to buy my aluminum plate I quickly snapped some photos with my cell phone, the owners don't like us to take pics because they are afraid we will steal their ideas. LOL
They are made out of stainless, this one is about 3' in diameter and 4 1/2' tall. the fire box is underneath and is about 1' in diameter and 1' deep, they use a 6"x12" steel pipe with 11/2" refractory cement on the outside and two holes on the bottom for a chimney starter (sold at another store), with tongs they take the burning coals out of the chimney and place them in the fire box through the door in front, it sells for $2,000.
Here's it big brother, it sells for $3,500.
And look what they have, a Weber Ranch, price $1,800, that's the big brother on the left so if you have ever seen a Ranch you have an idea how big it is. To the right is a Weber Performer that they have added a 3' extension with three grates.
On Sunday mornings they have a farmers market in the Marche, they also sell char siu and ribs that they smoke in these type of smokers, I have studied them and I don't see how they work without ventilation unless they open the top a little, but they smoke hundreds of pounds of pork in them, that is the reason I can't buy butts or ribs, they are all reserved months in advance.
Mrs JPT has promised to take some photos next Sunday, so if they turn out I'll post them so that you can see a little of how we live.