§ 27-b. Amortization of gains or losses. Gains or losses realized by the aggregate trust fund as a result of transactions made pursuant to subdivision two of section twenty-seven-a, or section twenty-seven-c of this chapter, shall be transferred to a special asset account to be known as the deferred charge on account of security transactions and shall be amortized within such account on a basis which matches as nearly as possible all gains or losses so realized against any increase or decrease in income resulting from the reinvestment of the proceeds of such transactions, provided that the period of amortization of the gain or loss resulting from the disposition of each investment shall not be longer than the unexpired period from the date of such disposition to the maturity of the investment so disposed of, or on such other basis as the superintendent of financial services may authorize in his discretion.