Victor kept meticulous written records of all of its recordings. The files cover the period 1903 to 1958 (thus including the RCA Victor era, as well as the Victor Talking Machine Co. era). These written records are among the most extensive and important sources of available primary discographic information in the world. There were three main categories of files: a daily log of recordings for each day, a file maintained for each important Victor artist, and a 4"×6" index card file kept in catalog number order.