I've remixed the design and removed the use of the hinge which for me wasn't working well.

I've added storage for the woods metal ingots with inspiration from the Lock Picking Lawyers new product the Replicator.

The melting spoon and lighter can be attached with a rubber band to hold everything together. I might look at neater solutions later, but for now this works well.

Creality

Ender-3 v2

Doesn't Matter

Doesn't Matter

0.2mm

30

Printed with ironing enabled to give a smoother finish between the parts.

1. Woods metal - sometimes listed as Cerrobend Pewtalloy Woods Model Metal
2. Sculpey clay
3. Baby powder
4. 1/2 teaspoon measuring spoon (metal!) / wax seal spoon
5. Flame - tea light works well

Load some sculpey into the tray and use a dull straight edge to level it out. I find the edge of the spoon handle works well. Scrape the clay along the top to get a nice perfectly flat mold.

Dust the clay with baby powder or similar. I use a cotton bud loaded with the powder to lightly brush some on. This allows the mold to release from the key being impressioned without sticking to it and ruining the mold.

Put the key in carefully and close the two halves. Apply pressure.

Remove the key. Close the two halves back together.

Melt some Woods metal in the spoon over a flame (no more than 1cm cubed is required generally which is less than a 1/2 of a teaspoon).

Once molten, pour into the mold. Give it a few taps to ensure it fills it well and then leave to cool for 5 minutes.

Remove and test!