I do want to mention the chassis does not look like a Rivarossi. I am not an expert by any means, however I have 2 rearward cab Mallets that are Rivarossi's and the articulation configuration is quite different. I have a Bachman N&W J model that looks more similar. The valve gear is also very different than what I'm used to seeing from Rivarossi also, more typical of Bachman. Either way NICE.
P.S. I mat be way off as I work in HO scale.