There is a 1961 color photo on page 64 of CLASSIC FREIGHT CARS, THE SERIES, VOL. 1 by John Henderson. In case you don't have this book, or can't find same, I will describe. The car has fairly simple lettering. To the left of the door it has SP&S and the number 10236, in sans-serif lettering with lines above and below. On the right is the SP&S oval herald, also sans-serif, which comes just short of the door stop on the left, and seems to be an equal distance from the individual grab irons which do for a ladder on the right. I'm going to say the herald's top edge is approximately 1-1.5 feet below the eves. The weight and dimensional data appear to be in the usual blocks we know and love, but the car is too far from the camera, and the print too small, to see this lettering clearly. I repainted and relettered one of my Ertl cars to this paint scheme.

What seems very odd about this car is that the journal box lids on the Andrews trucks are painted yellow. This probably denotes some restricted service, and think this may mark a car barred from interchange because of the Andrews trucks. Often in the 1950s yellow or silver journal box lids denoted a car fitted with roller bearings. I very much doubt that is the case here.

There is not enough detail in shadows to see if the car has AB brakes, but I suspect that is so.

The car appears to be all painted FCR, and the paint has faded somewhat. The roof appears to be bare galvanized metal. I have little doubt it was also FCR at one time, but the paint has all flaked away.

Just on a hunch, I dug through my clipped articles and found two photos in the December 1987 MAINLINE MODELER article "Boxcars of the Spokane, Portland & Seattle, Railway" by Ed Austin. Yes, the extra comma is in the title. A 1937 photo shows Railroad Roman reporting marks of  "S.P.&S. 10037" with lines above and below, plus all the periods. The Railroad Roman road name stacked is "SPOKANE PORTLAND" over "& SEATTLE" in the same spot to the right of the door as the 1961 car. Not particularly useful to your original request. The second photo shows a roofless conversion to woodchip service with a two-board extension above the car side, photographed around 1950. It is only lettered "S.P.&S. 39025" in Railroad Roman with lines, and no road name at all.