The best part of this jacket is that it's equipped with a real CLOWN zipper. The real thing costs nearly 10,000 yen even if purchased separately. Made of zinc-processed aluminum, its spring-adjusted movement is known for its smoothness, and it's the zipper used on the M51 jacket and M51 parka. Among others like Talon and Conmar, if it's an M51, it has to be Crown. Aiming for smoother operation, its complex structure made it delicate and prone to breaking, which is perhaps why it wasn't carried over to the successor, the M65, and the zipper manufacturer disappeared. If you know how to handle it, I don't think it's that delicate or easily broken. It's a rare zipper that disappeared in the history of zippers while pursuing smoother operation... This M51 jacket is from 70 years ago. It's from the time when Japan was booming with military procurement during the Korean War, when MacArthur led the UN forces and procured supplies.