The breastplate is in the Museum of Vienna (not the Kunsthistorisches Museum). My photos are taken from the thesis of Matthias Goll, which you can find online (very large document, with thousands of photos).
It seems to be a fairly basic, "munition" quality, infantry breastplate - doesn't appear to have ever been a lance-rest attachment. I'm curious to know if there is any resemblance with your breastplate... is it in your own collection, or one you have found in a museum or elsewhere?
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