The fact that most of the NWP's box cars were wood with friction bearing trucks means that few were still around by 1971 and most definitely could not be interchanged (because of the friction bearing trucks). The black car that Atlas is doing (thank you Atlas!) is the repaint of the Overnight cars that Mcjaco posted a picture of (previously ran by MT in two numbers, 1952 and 1953, now sold out), which is a repaint of the green Store Door cars (also ran by MT in two numbers, 1934 and 1946, now sold out...photos provided by ME!). These 22 cars were part of an order of 100 DS wood boxcars that were modified to also have steam lines so they could be used in passenger service (they were pulled in trains 3 and 4 as LCL fast freight to compete with Petaluma and Santa Rosa RR fast freight to SF). Atlas also ran two of the 'standard' paint cars in their first run of their 40' DS box cars (car nos. 1970 and 1973, now sold out). If anyone wants more info about these cars, just ask.
As for the cars that Aztec ran (thank you John), the NWP had 6 40' steel box cars (obviously former SP box cars since they kept all other standard SP lettering other than the road name and number) lettered for the NWP MW. These cars were mostly used as storage and rarely (if ever) moved. They survived until at least the '80 before they disappeared. Aztec ran all 6 of the cars (from photos provided by ME!). The cars were NWP MW 700, 702, 705, 706, 708, and 714. I have no idea what other cars were located in the number gaps.
As for anything else lettered for the NWP, that's just about it. World of Time did run a NWP baggage car (no 678, sold out). I've tried to get MT to run a caboose but so far they haven't (feel free to email them that you would like to see this done). MT has run two P&SR cabooses however (numbers 3 and 5, sold out). Other than that, that's it. Once again, thanks to Atlas for doing these not easy or inexpensive cars in N scale (full color small herald).
