Russ,
If this is 1968, the steam engine was being operated by "Cal Southern" (the shortened form for California Southern RR Museum) at the Perris site. The Santa Fe gon and the SP Caboose were from the OETM collection.
The relationship of California Southern RR Museum and Orange Empire Trolley Museum was a complex and difficult one. It can be a long story.
A solution was found in 1975 with the merger of California Southern into Orange Empire Trolley Museum and the resulting change of its name to Orange Empire Railway Museum.
The two ex-Army, ex-DOT Alcos that were acquired for utility (and not collection) purposes received the numbers 1956 and 1975 to honor the year Orange Empire was incorporated and the year of the merger.
Brian Norden
Orange Empire member since 1967