(15 ILCS 505/5) (from Ch. 130, par. 5)

Sec. 5. The Treasurer shall keep an official seal, which shall be used to authenticate all writings, papers and documents, required by law to be certified from his office; and copies of all records, writings, papers and documents legally in his keeping, when certified by him, and authenticated by his official seal, shall be received in evidence in the same manner and with like effect as the originals.

(Source: Laws 1873, p. 186.)