31 CFR 306.18 - Exchanges of coupon securities for registered securities.
Coupon securities presented for exchange for registered securities should have all matured interest coupons detached. All unmatured coupons should be attached, except that if presented when the transfer books are closed (in which case the exchange will be effected on or after the date on which the books are reopened), the next maturing coupons should be detached and held for collection in ordinary course when due. If any coupons which should be attached are missing, the securities must be accompanied by a remittance in an amount equal to the face amount of the missing coupons. The new registered securities will bear interest from the interest payment date next preceding the date on which the exchange is made.