I agree with Michael on the Duesenberg angle but wasn't totally sure with such a fuzzy picture (the tail has that look-IMO). If I had to hazard a guess I would lean more towards some of the early 1915 races on the west coast. Tom Alley drove a Duesenberg with the #2 in several races, where Marmon was also represented; San Diego Exposition Road Race (1/9/15), Tropico Race in Glendale (2/3/15) and the Vanderbilt Cup in San Francisco (3/6/15). Marmons ran in the first two contests but not the Vanderbilt cup so that may be suspect. As to the Holy Grail I am not sure I could ever give one example. There were too many great cars. There is not one that sticks out IMO.