(a) Beer of Puerto Rican manufacture coming into the United States and withdrawn for consumption or sale is subject to a tax equal to the internal revenue tax imposed on beer in the United States by 26 U.S.C. 5051.

(b) The excise taxes collected on beer of Puerto Rican manufacture shall be deposited in the Treasury of Puerto Rico only if the sum of the cost or value of the materials produced in Puerto Rico, plus the direct costs of processing operations performed in Puerto Rico, equals or exceeds 50 percent of the value of the beer when it is brought into the United States.