@bob2 posted:Agree with the Challenger and Big Boy - fine models, but undersize. Some say the Alco PA was scale size, but I have not been able to stand one up against MTH (exactly the same size as Key). I think the N&W Class A was full size, but it has a really narrow firebox. If a damaged one ever falls into my lap it will get 2-railed and a new firebox. The 773 Hudson may also be 1/4" scale.
The PAs are a hair short. I placed my Williams ones side by side with my Sunset ones and the Williams are about an inch short on length. I have a 1964 773 and when I place it next to my brass Williams one they are very close in detail and proportion. Obviously the tender from the 773 is not scale.