These 53'-6" flatcars were constructed with a welded fish belly steel frame in contrast to the cast steel GSI frame. The fish belly frame provided an optimal distribution of tension and compression forces from the center of the car to the bolsters. Think of it as a bridge. In addition, fabricating a welded frame was far less labor intensive than an equivalent riveted frame. The welded frame proved extremely durable holding up to rugged service. As these flat cars aged-out due to ARR interchange age limit, they found it's way into many years in maintenance-of-way service. A number of builders constructed these flat cars such as the Pacific Car & Foundry (P.C. & F.), Marine Industries (Canada), Pullman-Standard, Bethelehem Steel, and including railroad car shops such as the Western Pacific.

• Multiple car numbers for fleet owners for realistic train operations

Southern Pacific Class F-70-12 were built by Gunderson Brothers Engineering Company (GBEC) at their Portland Oregon plant for a whopping 1,150 car order. Delivered starting in Feb. 1962 and continuing into 1964.  They were assigned to general purpose use. Constructed with welded fish belly frames and Douglas fir decks treated with Pentha. Painted with Red Lead paint from Pacific Paint & Varnish or Freight Car Paint from Sherwin-Williams.

	Southern Pacific, GBEC 1963-1964, General Purpose Flatcar, Class F-70-12, Stencil date 3-75, ACI label; 6 car numbers
50147	SP 564313
50148	SP 564352
50149	SP 564521
50150	SP 564809
50151	SP 564940
50152	SP 565047
50189	SP 3-pack   (Random Number)
50190	SP 6-pack   (All 6 Numebrs)