Small octagonal (8 sided) two part jewelry or nick nack storage box, 145mm (5 ½") diamater x 1.8cm (¾") high (internal dimensions) storage box. One octagonal box fits over the other.

My wife has a prized gold choaker/neclace which cannot be bent and is best laid flat when not being worn, so I made this for her to both store the neclace but also to add earings or rings if we went away so it was safe in her bag. Even though the two boxes slide over each other easily and grip each other well enough. so the two pieces are extremely unlikely to come apart, it has small indents in the octagonal top and bottom faces so an elastic band could be put around it to prevent them coming apart, if you wanted more piece of mind.

I have included both STL and 3MF files. I printed one piece at a time because both would not fit into my Bambu Lab X1 Carbon at one time. Each took just over an hour each to make at 0.16mm layer height. I used PLA but it could be made from many filament types and it is absolutely trouble free to print. No other parts are necessary, unless you want some thin foam in the bottom.