California Code, Health and Safety Code - HSC § 4790

The bonds shall be signed by the chairman of the district board, and countersigned by thecounty treasurer, and the seal of the district board shall be affixed. The interest coupons of the bonds shall be numbered consecutively and signed by thecounty treasurer. All such signatures and countersignatures may be printed, lithographed, engraved, or otherwide  1 mechanically reproduced except that one of said signatures or countersignatures to said bonds shall be manually affixed. Any such signature may be affixed in accordance with the provisions of the Uniform Facsimile Signatures of Public Officials Act, Chapter 6 (commencing with Section 5500) of Title 1 of the Government Code.