I bought these two MTH box cars from Sidetracks. I asked for the scale wheels, so owner Tom Henderson removed the AF-compatible couplers and installed the MTH scale wheels and trucks. So for a nickel short of $50 we have another box car to add to our layout. People are complaining about how expensive MTH's equipment is, but these two cars are among my cheapest acquisitions. The cars don't come with couplers, but I am going to be installing the Walther ProtoMax couplers anyway.
The MTH cars are every bit as good as the original S-Helper Service cars. The doors open, and the underbody detail is exactly what S-Helper Service use to do. Even though both cars' road numbers fit within the N&W B6 class, they don't have the "B6" text in the lower, right-hand corner that the prototype photo I've found shows. I don't have a prototype photo of these exact road numbers, so perhaps they didn't have that lettering. However, doing a bit of work on the decals should not be a problem down the road. Overall, I think these are very nice models. They ride and track very well. I have had no derailments with them on either my home layout nor on our club layout.