Railway Metal Products, Union Metal Products, and Standard Railway Equipment were all related companies by 1927, according to this Railway Age note:
"The Standard Railway Equipment Company, the Union Metal Products Company, and the Railway Metal Products Company, have moved their offices from the Railway Exchange Building to the Shell Building, St. Louis, Mo. A. G.Bancroft is southwestern sales manager, and E. G. Fredell service engineer, at St. Louis. "
There is also this note from June 25,1919:
"National Car Door
ONE OF THE DEVICES exhibited on the pier which has been developed since the last convention is the National car door. This door is supported directly on the underframe on rollers of large diameter, mounted in brackets which do away with the track. This method of support was adopted to place the weight of the door at the point where the distortion of the frame would be a minimum. The rollers themselves are designed to prevent freezing up with snow or ice and can be loosened by a slight jar in case they clog. The bottom of the bracket is opened, permitting any foreign matter to fall through. The door being supported at the bottom brings the handle close to the line of support and prevents binding or cocking.
The top interlocking feature is so arranged that snow and ice cannot accumulate and prevent free movement of the door ; with the front and back interlocking connection to the door post it forms a weather and spark-proof construction. By the use of beveled rollers in the brackets the door when shut is kept tight against the car. Flat rollers and a lug on the brackets keep the door away from the car when open, preventing binding and injury to the sheathing and insuring easy operation. This door is built by the Union Metal Products Company, Chicago, and has been specified for application to the entire 25,000 double sheathed box cars ordered by the United States Railroad Administration."