This is an antique lock from the Joseon Dynasty (Yi Dynasty), with an inscription (see photo 11). The inscription is written from right to left, reading "Seikin" (成金) and "Kim Seong" (キム・ソン) from right to left, possibly the name of the lock maker. I believe this lock is more difficult to open than the Joseon Dynasty antique locks, part 1 and part 2, that I previously listed, which have unique unlocking methods. Regarding this lock, I would like the buyer to experience the trial and error and the moment of unlocking, so I will omit explanations about unlocking. It may not be difficult, and it may not take much effort, and you may be able to unlock it in a flash. In this case, I hope you will appreciate the ingenuity of the structure, such as the three-dimensional shape of the key and its engagement with the leaf springs. The leaf spring part of the lock offered this time has a structure that is rarely seen elsewhere. As seen in photos 11-15, four thick spring materials are arranged in a columnar shape, and the edges are characterized by "fitting" and "jagged" processing. I don't know the exact reason why this processing was done, but perhaps it was to make the locking mechanism stronger and more robust? The material is copper or a copper alloy, but when it was made (age) is unknown. There are stains, green rust, and scratches, but there is almost no deformation, and the robustness is well preserved. The approximate size (cm) and weight are as follows: [Lock] Width 8.9, Height 3.3, Depth 2.2 / Locking area 5 x 0.9, Shaft diameter 0.3 / Weight 155g / [Key] Length 16.5, Width 1, Weight 20g / Please try to unlock it. When unlocking, do not use too much force when inserting the key, and if the lock does not release immediately, try inserting and removing the key several times. You will definitely be able to unlock it. Please be careful not to lose the key.