In 1963, during American Express's Salad Oil Scandal, Buffett visited restaurants to see how people used the American Express card, an approach he first used then.

Factual claim about Buffett's own history, judged as of 27 February 2017. The test is that during the American Express Salad Oil Scandal (which became public in late 1963) Buffett did 'scuttlebutt' field research, such as visiting restaurants or businesses to watch whether customers kept using American Express cards and checks, and that this was the first time he used that approach. True: biographies (for example Schroeder's The Snowball, Lowenstein's Buffett) or contemporaneous accounts confirm the field research in 1963–64 and nothing contradicts it being his first use. Mostly true: the research is confirmed but a detail differs (it mainly took place in 1964, or it covered banks and travel-check outlets rather than restaurants). Mixed: the research is confirmed, but credible sources show he had clearly used the same approach before. Mostly false: Buffett invested in AmEx during the scandal but the field-research account is unsupported or is significantly different. False: the evidence shows no such research took place.

Set before the research began.

1. E1 1964 Warren Buffett Partnership Letter — Buffett Letters · Chian Chian.io (Buffett Letters knowledge base)

   “Buffett explains how he conducted research — talking to employees, customers, and competitors ('scuttlebutt') to confirm the core charge card business remained intact despite the scandal.”

2. E2 Salad oil scandal Wikipedia · 11 August 2007

   “On November 15, Allied was informed that its activities in the futures market were being investigated by the Commodity Exchange Authority.”

3. E3 Salad oil scandal Wikipedia · 11 August 2007

   “American Express stock dropped more than a third, reducing overall value by $80 million.”

E1 is a third-party summary of Buffett's 1964 partnership letter. It says he did "scuttlebutt" research, talking to employees, customers and competitors, to confirm that American Express's core charge-card business was still intact despite the scandal. This supports the claim that he did field research during the scandal. E2 and E3 confirm the scandal itself and AmEx's sharp stock drop. No evidence here confirms the restaurant visits or the 1963 timing, but nothing shows he had used the approach before. Because E1 is an undated summary that does not confirm the restaurant visits or the 1963 timing, the verdict is mostly true rather than true.