Inner core (width) dimension: 54mm Inner (depth) dimension from the core: approximately 10.7mm 3 keys I found and purchased it at a general goods store. It was stored in a storage room. I can confirm its operation if you wish. I liked the design, which looks like it came out of a historical drama (Meiji, Showa era), and the Bulldog mark, so I obtained several as a collection. After researching, I found out that it's discontinued.