The HO Scale Brass 4-6-6-4 Challenger Steam Locomotive Rio Grande #3707 is a highly detailed model steam locomotive in 1:87 scale. Made of brass with a black color scheme, this vintage locomotive features the iconic 4-6-6-4 wheel configuration and is graded as C-4 Fair. Perfect for collectors or model train enthusiasts, this locomotive captures the essence of the Rio Grande railroad with its attention to detail and historical significance. Not tested.