We are restoring the windows at Hamilton Hall in Salem, MA. From their website (www.hamiltonhall.org)
Hamilton Hall in Salem is widely recognized as one of the most important Federal buildings in America. It was designed in 1805 by the famous architect and master woodcarver, Samuel McIntire, and has been in use as an assembly hall for cultural and social events for over two hundred years.
In windows of this vintage, the construction is different from what became more standardized after 1850. Rather than the front stop being set inside the jamb, the stop is actually flat to the window. It’s a handsome look, but does not enable you to adjust the fit of the window like you can with the later variation.
Here the front stop that holds the window in place is installed to cover not just part of the window stile but also the window framing. There are small clips on these particular windows for interior plexiglass panels. In the second photo you can see that to remove the stop you have to pry it away from the side. The back side of the stop is bevelled.