Don,
That can be a problem argument. One must be careful I think with,
"X existed there, earlier, and folks who had been there came here, so here there should or could be some of X as well." While an article may exist in a location at a specific era, the passage of time and contact with that area do not necessarily mean an item of material culture would be transported. Time sometimes causes the opposite..., causing an item that did journey to a new location to disappear, and there's no way of predicting which result will occur.
So there was contact with China in the 18th century, first by the Portuguese, and then heavy contact by the British between the FIW and the AWI. YET, even though it is a very efficient cooking utensil the Wok did not appear in 18th Century British cooking, nor did Chinese recipes. Curry did appear, but not something like Hunan or Szechuan cooking style nor food.
AH but there is a difference when you take the actual people and the material culture move them to the new location. This is quite true..., had the British taken Chinese people to the colonies, just as the Chinese later moved to California in the 19th century, they would've brought their culture with them and likely tools and utensils, but in the case of a wok, that item never declined in use. It's still used today....
The Scots had used that type of dirk a lot in the 17th century, but for various reasons that combined in the 18th century, the use had dropped off, and thus the making of such dirks also reduced over time, and the existing dirks then would also have declined in use, due to wearing them out or avoidance of penalties, or both. Another good example of this would be the
targe.
David Morier painted this image in the 18th century..., The Scots are seen in the image with no less than 5 targe...,
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So YES a person could have such a shield more than a century later in the American Colonies, but the use of them had dropped off, and I doubt folks would think them a good idea on a latter 18th century battlefield. You can carry the idea further, with armor and bows that could have survived and did. In fact Ben Franklin thought that longbows might be a viable weapon if there was a musket or gunpowder shortage, and armor chest plates were worn in Europe by some cavalry troops into the 19th century, but I doubt that anybody would suggest that a person taking part in a colonial living history setting should wear 17th century archer's armor and use a long bow...
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LD