The mint in San Francisco produces collectibles instead of cranking out our actual spending money, and that means it brings in big business for the U.S. Mint, as collectors are happily pay premium prices for perfect proofs and commemorative coins. Run under heavy security, the mint is closed to the public, but allowed a special tour for delegates to the XXIII Mint Directors conference and some news media on Tuesday. The last public tour was in 1993. Armed guards kept an eye on the visitors as they were shown stamping and packaging machines. The mint is celebrating 150 years in San Francisco.