The Heritage big bore revolvers are made by Pietta. Heritage makes the rimfire guns in the US. They make two kinds of rimfire revolvers - one is steel, the other is that Zamac "pot metal" with various sleeves where extra strength is needed.
The big bore revolvers ought to be whatever Pietta is producing as an 1873 clone. I wouldn't expect any non-steel or brass parts that aren't in their regular line, but I suppose that depends on just how finished the gun is before Heritage gets it.
Well we don't rent pigs and I figure it's better to say it right out front because a man that does like to rent pigs is... he's hard to stop - Gus McCrae