The reiteration of an Outperform rating and a maintained price target of $64 by a reputable analyst like Gary Prestopino from Barrington Research is likely to instill confidence among investors and could lead to a positive short-term impact on Koppers Holdings' stock price. Analyst ratings, especially those that are positive and come from well-regarded financial institutions or analysts, tend to influence market perception and investor sentiment, potentially driving up the stock price in the short term.