Secondary evidence defined to include certified copies, machine-made copies, oral and written admissions and expert examination evidence. Section 58 defines secondary evidence to include certified copies produced under the Act; mechanical-process copies that ensure accuracy and copies compared with them; copies made from or compared with the original; counterparts against non-executing parties; oral accounts of a document's contents by someone who has seen it; oral admissions; written admissions; and testimony of a skilled examiner when originals are voluminous and cannot conveniently be produced.