In regards to armour and the material it is made of -

We as a rule strive for historical authenticity, we also should note that none of us can ever be completely authentic. We may have wool clothing, but it is not necessarily made of the same quality wool that was available in the Middle Ages, nor as a general rule do we use hand loomed wool (although we do if we can lay hands on same). So it must be with harness.

Most groups allow inaccuracies that are not visible to the naked eye, as an obvious for instance most helmets on the field are made in two halves and welded (most groups want that weld to be invisible). The material of the harness itself is one of the areas that we have to compromise because the original quality material is simply not available. Historically in the 15th c. plate harness was made up from billets (or more commonly in Milan or Innsbruck sheet from hammermills) of wrought iron or low carbon steel. One of the chiefest differences is the original material has slag inclusions - modern steel is homogenous. Antique wrought iron can be obtained, but I was assured Saturday by no lesser personages than Dr. Walter Karcheski and Robert MacPhereson that the wrought iron of the 18th & 19th centuries is still substantially different than Medieval wrought iron in composition, so even going to that length is not completely accurate.

That said, modern mild, low, and mid carbon steels are the material amongst the readily available materials that most closely resemble both in look and preformance the original material. Stainless to even a generally trained eye sticks out - it is too white. Not only that, but the spirit of our quest is to be as close to the original when we make an item as we can. Modern homogenous steels are to us what computer operated loomed wool is - an acceptable alternative, not as good as the original, but what we can reasonably achive. Stainless to us is what synthetic cloth is - a readily apparant anachronisim that is not in the spirit of what we are trying to do, which is the most authentic appearance we can muster.

When it really stands out is the wear a piece sees in the field. Stainless steel by it's very virtue lacks the appeal as it will not resemble a working harness in use (although it makes a great costume). We want the full affect, and that includes equipment maintanence (makes great demo's in the field). If i could get a raised helm of non-homogeneous steel, slag inclusions and all, I would choose that option. To the best of my knowledge, the people with the skill to most closely duplicate the original artifacts shape do not work with this material, it is not readily available to them, and the scrap material that it is made of would still not be authentic (but it would be a step closer).

There is nothing held against stainless in most martial sport groups, but to most living history groups it is not acceptable. I hope this clears up where we are coming from.