The First 500 book covers the part differences from the First 500 1911 pistols issued to the 1911A1. There are photos of the original parts and the 1911A1 parts to visibly show the differences. Cylinder & Slide printed this book so that those who were interested in purchasing our 1911 Anniversary pistol would understand that the Anniversary pistol had the original parts that were in the first 500 1911 pistols issued to the Army.This is a great reference book for those who wish to authenticate original 1911 parts.