I checked it out.
There seems to have been a switch of sides some time in the mid 19th, century.
All through the 18th century, the majority of dresses seem to tie with laces. Those dresses with button holes, go left over right; just like men's shirts and coats. I saw one dress that was right over left but it was double-brested - with two sets of overlarge buttons going down the front, looking more like decorations than closure.
From what I can see, the right over left for women started in the mid 19th century whem more women's clothing were made with buttons. Starting then, they all go right over left. There's no explanation for this in the book unfortunately.
I think I'll write the museum and ask. Their address is in the book.
