Diane Wolfgram commented:

At least 210 of these were built in 1914, too.  Ownership was split, primarily, between the Southern Pacific and the lines that were later consolidated into the Texas & New Orleans.  All told, the PS received 150 of them and the T&NO and other Texas-Louisiana Lines 700 of them.  The Northwestern Pacific got 20, the Pacific Electric 10 and the SPdeMexico 26.  320 of the total were constructed by Standard Steel Car (SSC).

From a modeling standpoint, notable differences between these and the later S-40-5 class were that the -4s rode on Andrews trucks while the -5s had Vulcan trucks.  The -4 had a low, horizontal sliding "feed" door on the B end, but there wasn't any on the B end of the -5s.

I don't carry all this around in my head, but do keep Tony Thompson's Southern Pacific Freight Cars, Volume 1 within reach much of the time.