COOL! (pun not intended)
Might want to preheat the mould on a hotplate (put a metal disk on it to even out the heat).
I assume that the base plug drops in and out - looking at the retaining tab.
When designs look simple the designer put lots of time in the THINKING it out stage.
That also gives you options for several baseplug designs.
I heated the mould by sitting it on top of the pot as the lead melted. Sometimes I use a torch. This mould has a lot of mass, so it takes longer to heat up (which can be a good thing, since it doesn't cool down as fast between pours). I tried using heavy welding gloves, but manipulating the mould parts was difficult. I went to thinner gloves, and that was no good either (Owwww!). Need handles.
Yes, the tab can be swung to the side using the tip of a tool in the little dimple, then pried loose via the slot.
For something that won't be used all that frequently, simple is good. I've made way too many fancy things that sit on a shelf for decades.
DoktorD - Yes, it's lead.
