Back then, Santa Fe's numeric symbols reflected the regions of origin and termination (first and third digits) while the middle digit was the type of train. Since the train in the photo was an eastbound pig, it may have been the 991: origin of northern California=9, intermodal train=9, destination of Chicago area=1. The westbound counterpart was the 199--opposite direction, but still an odd number. Since southern California was region 8, the Los Angeles-Chicago counterpart would be 891 eastbound and 198 westbound. The daily Richmond-Barstow junk train was the 928. The odd thing was that the symbols only indicated regions, not specific terminals. You just had to know which trains went where.