Based on the hairstyles of the nyphs. I did a stint at the ren-fair here
for about 10 years. There is nothing that gives a decade away more than the
hair. The early dates are is the ms is mainstream, the latter if the ms is
provintial. I have not done a lot of study on the era. (My main intrest are
the time from 1770 to 1870 with the emphasis on the mid point late 30s
early 40s, which is where the real progress in mechanics were made, but
then I digress, see Charles Dicken's for more details).
What the costumer does have to work with are paintings and drawings
attributed to a given era. Many of my books cover wide ranges of times.
Back when I joined the list, I was asked this so I took some time and
scanned through my copy of petersen and my costume books. Granted much of
what is recorded is upper class so if things are provintal they may relate
to an earlier date than the mss.