(2) A right which is in substance economically equivalent to a production payment shall be treated as a production payment for purposes of section 636 and the regulations thereunder, regardless of the language used to describe such right, the method of creation of such right, or the form in which such right is cast (even though such form is that of an operating mineral interest). Whether or not a right is in substance economically equivalent to a production payment shall be determined from all the facts and circumstances. An example of an interest which is to be treated as a production payment under this subparagraph is that portion of a royalty which is attributable to so much of the rate of the royalty which exceeds the lowest possible rate of the royalty at any subsequent time (disregarding any reductions in the rate of the royalty which are based solely upon changes in volume of production within a specified period of no more than 1 year). For example, assume that A creates a royalty with respect to a mineral property owned by A equal to 5 percent for 5 years and thereafter equal to 4 percent for the balance of the life of the property. An amount equal to 1 percent for 5 years shall be treated as a production payment. On the other hand, if A leases a coal mine to B in return for a royalty of 30 cents per ton on the first 500,000 tons of coal produced from the mine in each year and 20 cents per ton on all coal in excess of 500,000 tons produced from the mine in each year, the fact that the royalty may decline to 20 cents per ton on some of the coal in each year does not result in a production payment of 10 cents per ton of coal on the first 500,000 tons in any year. Another example of an interest which is to be treated as a production payment under this subparagraph is the interest in a partnership engaged in operating oil properties of a partner who provides capital for the partnership if such interest is subject to a right of another person or persons to acquire or terminate it upon terms which merely provide for such partner's recovery of his capital investment and a reasonable return thereon.