19 C.F.R. § 159.34
(a) Countries for which quarterly rate is certified. For the currency of each of the following foreign countries, there will be published in the Customs Bulletin, for the quarter beginning January 1, and for each quarter thereafter, the rate or rates first certified by the Federal Reserve Bank of New York for such foreign currency for a day in that quarter:
Australia, Austria, Belgium, Brazil, Canada, Denmark, Finland, France, Germany, Hong Kong, India, Iran, Ireland, Italy, Japan, Malaysia, Mexico, Netherlands, New Zealand, Norway, People's Republic of China, Philippines, Portugal, Republic of South Africa, Singapore, Spain, Sri Lanka (Ceylon), Sweden, Switzerland, Thailand, United Kingdom, Venezuela.
(b) When certified quarterly rate is used. The certified quarterly rate established under paragraph (a) of this section shall be used for Customs purposes for any date of exportation within the quarter, except in the following cases:
[T.D. 73-175, 38 FR 17482, July 2, 1973, as amended by T.D. 81-117, 46 FR 24944, May 4, 1981]