30 ILCS 425/7
Bonds shall be signed by the Governor and attested by the Secretary of State under the printed facsimile seal of the State and countersigned by the State Treasurer by his manual signature or by his duly authorized deputy. If Bonds are issued in registered form pursuant to the Registered Bond Act, the signatures of the Governor, the Secretary of State and the State Treasurer may be printed facsimile signatures. The Master Indenture or any Supplemental Indenture may also require that each Bond be authenticated by the manual signature of the trustee thereunder or of a registrar or paying agent. Unless Bonds are issued in fully registered form, interest coupons with facsimile signatures of the Governor, Secretary of State and State Treasurer may be attached to the Bonds. The fact that an officer whose signature or facsimile thereof appears on a Bond, interest coupon, indenture or agreement authorized under this Act no longer holds such office at the time the Bond, coupon, indenture or agreement is delivered shall not invalidate such Bond, coupon, indenture or agreement.
30 ILCS 425/7