Sporran maker?

[Alba]

OK, I'll try again as people don't seem to understand the question. Polishing brass is fairly obvious. The question is what was the black paste that hardened and gave old leather sporran cantles faces their shiny facade. It was clearly an applied application as it tends to warp, flack and run or time. Not sure if this is due to temperature, humidity or what, but the effects are obvious on older military sporrans. Below are some images of what I'm talking about. (I hope. First try adding pictures)

You will note how the leather can be seen under the past on the old Cameron Highlander (Canada) sporran cantle. And how its deformed around the Scots guard one and bubbled on the Cameron Highlanders piper sporran cantle.

You will also note how it's adhered to the Cameron badge of a different cantle. So it's obvious a paste of some kind that was brushed on. The question is, what was?

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