30 ILCS 330/10
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. 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 or interest coupon no longer holds such office at the time the Bond or coupon is delivered shall not invalidate such Bond or interest coupon.
30 ILCS 330/10