Steve Prefontaine in Adidas gear, probably at the July 1972 Olympic Trials, at Hayward Field in Eugene, Oregon.
This photo was for sale online by a dealer in vintage photos and papers of notable people. The description said that the photo was marked on the back with photographer Stan Pantovic's business stamp, and a date of 1975. The date is either in error, or misread for some reason. This could not possibly be Pre in 1975--he wore Nike gear exclusively beginning in April 1973 until his death.
Pre first showed signs of peach fuzz on his upper lip at the June 1-3, 1972 NCAA championships. The next and only remaining Eugene meet in 1972 was the July Olympic trials when he had a mustache that closely resembles the growth he shows in this photo. I'm guessing he wore the t-shirt for a short while to show the Adidas name and that's when Stan took the photo. By the spring 73 meets in Eugene, Pre had a pretty bushy mustache.
This display by Pre also provided an opportunity for him to tweak the nose of the Amateur Athletic Union, the draconian, oppressive and arbitrary overseer of all things amateur athlletic in America, and which banned amateurs from wearing corporate and product symbols on their track apparell. He sports a somewhat defiant look.
Stan Pantovic was a free lance photographer who contributed to Runner's World magazine, and other publications on occasion.
Pre almost always wore Adidas through high school and most of his college years, switching to Nike's after the start of the spring 1973 outdoor track season, when Pre was an Oregon senior.
This is the only photo of Pre I've seen with him wearing an Adidas top and shoes--other images show him in Adidas warmups with high school or college track suits.