I bought an Optimus stove new in the 80s when I first went camping under my own steam. The 'hob' plate was painted – a goldish colour IIRC. The paint didn't last 5 minutes once the stove was lit.
If you have not already found it, there is at least one forum dedicated to these things – https://classiccampstoves.com/
I'm pretty sure that the enamel on the tops of Tilley lamps is kiln fired… a pity because I think you can only get black ones now but my older lamp has a brick red one that is somewhat rust eaten.