; conclusiveness and validity of guarantee (1) Full faith and credit of united states pledged for payment The full faith and credit of the United States is pledged to the payment of a note or other obligation guaranteed under this section. (2) Conclusiveness and validity of guarantee (A) Conclusiveness A guarantee made by the Secretary under this section shall be conclusive evidence of the eligibility of the obligation for the guarantee with respect to principal and interest. (B) Validity The validity of a guarantee made by the Secretary under this section shall be incontestable in the hands of a holder of the guaranteed obligation. (3) Limitation on percentage A guarantee made under this section shall guarantee repayment of 100 percent of the unpaid principal and interest due on the notes or other obligations guaranteed. (h) Taxation of interest; grants to issuing participating jurisdiction