Nason Railways produced freight trucks in three basic designs, Vulcan, Dalman, or Andrews. The truck on the left is the Vulcan type, with four springs visible. The Dalman was a somewhat heavier looking design with two visible springs. The Andrews type has the characteristic extra piece on the bottom of the journal box. All are sand cast bronze.
One selling point was that these trucks were sold completely assembled. They are seen with two different bolster designs. In the photo the Dalman and Andrews trucks have a fiber bolster that has tabs that were attached to the truck sideframes with screws. The Vulcan truck however has a square bolster that is pinned onto a peg on the back of the sideframes. Click on the photo to see this more clearly. Note also that the truck in the middle has wheelsets a prior owner worked up from 3 rail Lionel wheelsets. They cut the axle and used plastic tube to hold the gauge, in the manner of the Nason wheelsets seen on the outer trucks.
From the catalog copy I cannot determine if any one truck was sold always with any one model. If anyone has insights on this based on instruction sheets I would love to hear from you (As of this writing I don’t have any freight car instruction sheets for Nason in my collection).
UPDATE: Reader Dick Gresham filled in a couple details of note. One would be that the three rail version of these trucks have a brass bolster, not fiber as in my photo, and he supplied a photo of the three rail truck. The second would be that the flat car instruction sheet (click for link to PDF version) does not specify any specific type of truck. Most likely the other freight cars are the same, they could be shipped with any of the three styles of truck.
Also note in his photo: Tru-Scale track with the self-gauging roadbed, a staple of OO gaugers of the past, available before and after WWII. My track is in contrast handlaid with modern code 100 rail.