Footwear in Highlanders of Scotland

[Tobus]

Richard, since you seem to possess some high-resolution images of MacLeay's portraits, maybe you could help me. I have been looking closely at examples of Victorian footwear, hoping someday to find a pair of nice ankle boots that would come close to some of the examples I've seen. But one thing which jumps out at me about MacLeay's portraits is that some of the wearers appear to have on shoes or boots with heavily hobnailed bottoms. Or even what appears to be a solid metal studded toe plate.

I only have two examples with resolutions decent enough to see them, as shown below. But you may have better images to look at. Do you see other examples in his portraits of these types of soles on their footwear? Have you any idea what this is?

A casual assumption would be that he's just showing a typical leather bottom with hobnails. But he seems to clearly paint them silver, where many of his other shoe examples are in a more realistic shade. He would often put a bit of glare on the fronts of their leather soles, appearing as a silver-ish hue for the glare, but nothing like these examples which seem to show bright metal bottoms. Do you think he is portraying an actual metal studded plate, or is it just an error on my part in interpreting?

I don't see any examples of soles like these in actual kilt photographs from the era.