So this is a debate that comes up often in my circle of friends. We are medieval enthusiast and most of us fight in late 14th century period armor. A focus of our group is historical accuracy, and translating/interpreting the fight books, manuscripts and effigies of those periods to understand how armor worked and was fought in.
One thing I try to encourage to anyone in the group is basing your 'harness' off of extant museum pieces, effigies or manuscripts to help ensure that certain pieces will function properly together. I.e a gothic helmet and bevor don't always work right with a transitional period breastplate.
That said, this question comes up often: How realistic was it that regional armor styles made their way around Europe?
Most effigies represent regional trends and fashions, and it stands to reason that a person would go to the local armor smith rather than import the armor. However Europe is not as big as many of us Americans make it out to be in our mind. Salzburg to Milan is roughly the same distance as Kansas City to St. Louis.
I've changed my position on this over the years. I believe it is not unreasonable, given the amount of trade and mercenary work that was happening in the time, to see a French Knight wearing something that might be considered more of an Italian style. I don't think this was the norm by any means but given that our concept of nationalism wasn't yet a thing, I could see soldiers from modern day border regions adopting fashions that are more geographically fluid than we think of today.
If anyone has an insight into the trade and proliferation of cultural fashion and/or armor I would be very curious to hear about it. If you have any sources that would be fantastic.
Thanks for your time.
This is indeed a common question among reenactors who have to concerns ourselves with the proper 'look' and construction of armour and weapons. The question is not just 'what did armour look like' but 'who wore it' and how - put differently, how did armour fit into its cultural context - the economics, military history and fashion of late medieval Europe.
I speak about armour and fashion here in terms of time, but what I said could just as easily apply to place. Armour, like other arts, takes its inspiration from the aesthetics of the culture that produces it and the culture that consumes it. The second part is particularly important because it was they who drove the demand for armour, and that means it was often their fashions that dictated what kind of armour they would buy.
Armourers were indeed sophisticated businessmen serving a market that spanned the continent - the armourers of Milan in particular sold to nearly every corner of Europe, and other centers like Cologne or Nuremberg could sell armours across lengthy trade networks. I talk about the international nature of the armour industry in these answers:
But while armourers were selling to international markets, they also seem to have quickly learned to tailor their wares to their customer's tastes. These could vary quite a bit - in the mid and later 15th century each European country or region had its own stylistic preferences, as I discuss here. Moreover, armourers were very well aware that different regions (and yes, even different people) had different stylistic preferences, so they were very capable of making armour in different styles as I discuss in that previous answer. For the outstandingly wealthy who could afford custom harnesses, this could include ordering armour in the style of your own country from a forieng armour, or ordering armour in the style of a neighboring country from an armourer (in the later 15th century we see some effigies of English Knights whose armour looks very 'French' in style - Italinate with arming garments worn over the cuirass). For those offering harnesses 'off the rack' or in bulk, they could turn to the armours made in Milan according to local tastes - generally called 'Italian Export' by armour historians today. A specific sub-style of armour for export is the 'alla tedesca' harnesses (roughly, 'in the German style') which imitate contemporary armour fashion in the German lands.
An added wrinkle to this all is that even if the 'hard' parts of a harness ('suit' of armour) were taken over the alps from Italy and sold in france without any allowance for local fashion, a French man at arms would still wear the armour in the fashion of a Frenchman - in the later 15th century, this would include a sallet, less full mail than was worn in Italy, and plate sabatons rather than the Italian mail slippers.
The upshot of this is that the origin of armour doesn't entirely determine the overall style of the armour, especially when it is actually worn. This means that though we do indeed see a lot of Italian armour being shipped all over Europe that doesn't mean that Italian armour -style- was shipped all over Europe whole-hog. Instead, it had a massive influence, but other regions had their own preferences. So even a very 'Italinate' armour in France wouldn't look like it does it Italy.
Moreover, we have to look at the evidence we have - we already have a lot of evidence for people wearing different styles of armour because we have a variety of high-quality depictions of armour (mostly full relief effigies but also brasses and paintings - I find manuscript miniatures are often hit-or-miss and frequently very stylized). By looking at a lot of examples of art in a certain medium (IE effigies) from one region and period we can start to see the diversity of styles that are present - this is how I noticed the 'French' style armour on some English effigies. However, we can't really say much about what we -don't- see, and while absence of evidence is not necessarily evidence of absence, my feeling is that we have to follow the sources we have.