MIL-HDBK-57C, DEPARTMENT OF DEFENSE HANDBOOK: LISTING OF FASTENER MANUFACTURER'S IDENTIFICATION SYMBOLS (5 APR 2007)., This handbook is a compilation of the identifying symbols of fastener manufacturers as provided by the manufacturers themselves. This issue contains the names, addresses, and the symbols of all fastener manufacturers whose identifying symbols were received by 30 November, 2006. Each manufacturer who was listed in Revision B of this document was contacted to confirm the accuracy of the published information. We have annotated the listing to indicate those manufacturers that have responded to confirm or update appropriate information. The listing also annotates which manufacturers have not responded. Information about manufacturers who have not responded is still maintained in this latest revision. For the purpose of this handbook, a manufacturer is defined as the source which substantially makes the supplies, either by hand or machinery out of raw materials. Fasteners, as defined for the purpose of this handbook, refer to those threaded items included in Federal Supply Class (FSC) 5305 - Screws, 5306 - Bolts, 5307 - Studs, and 5310 - Nuts. As additional manufacturers submit their markings, the handbook will be updated.