Questions and Answers about Japanese' (published by the National Institute for Japanese Language in March 2001) listed various theories of counting two pieces as one kan, but described that the theory of counting one piece as one kan was persuasive.
「言葉に関する問答集」（国立国語研究所2001年03月）では、2個1かんの諸説を挙げた上で、1個1かんが有力としている。