Two Verwundetenabzeichen and an Allgemeine Sturmabzeichen.

[Adrian]

I know with some types of metals, they begin to pit as they age. Whats a good way to tell the difference?

That is true, pitting can occur as a result of deterioration of the base metal but in this case the pitting is caused at point of manufacture by the casting process. Air bubbles come to the surface, burst and leave the pitting effect. Contraction of the metal as it cools from liquid to solid can also result in an uneven surface too.
I'm sure someone who knows a bit about the technical and scientific aspect of this can shed some more light on my basic explanation.

[bradanimal]

Adrian, makes sense. Thank you. So for the deterioration pitting, I'd need to look for a different color of the pitting compared to the surrounding metal?

[Adrian]

Rust can leave pitting and is quite easy to spot on ferrous metals. Zinc on the other hand is non ferrous and the pitting found on zinc items is usually down to atmospheric conditions, the environment in which the item is stored, humidity etc. The condition known in collecting circles as 'zinc pest' which I think is a form of white rust which forms on zinc can also leave pitting. If the quality of the zinc is poor and other elements are in high concentrations within the alloy, these may deteriorate over time and leave pitting or an uneven finish.
I'm no metallurgist so my understanding of the subject is poor at best so maybe another member can go into greater detail.