The Straco Express had clear markings on it, which allowed me to find some background information about the toy. It also had fairly sophisticated metalwork. The engine required quite a bit of hand assembly, and each of the three cars were constructed in a different fashion, requiring mostly different tooling.
My childhood Santa Fe, however, was a different story. As near as I can recall, the set always only had three pieces -- the Santa Fe diesel, vaguely resembling an F3, and two box cars. No caboose.
I have yet to find anything about this set either online or in reference books available. Clearly it was made in Japan, most likely in the late 1950's-early 1960's. Did the FJ Strauss company (who had the Straco Express made for them) also make this set? There's no markings anywhere, save for a small marking on the back of the engine saying "Trade Mark Made in Japan."
If anyone has information about this set, I'd love to know more. Was it the same Japanese company making toys for two separate American importers? That's my guess, but I'd really like to know for sure.