"Old school" is the only way to do these. They were handcrafted the first time, and are again this time.

I specialize in houses built before 1950, particularly single wall and hybrid construction. But this is a stretch for even me. I would lay odds that there are only a handful of people left in the U.S. who know how to build historical wooden sash windows by hand (and by hand I mean BY HAND, you can't buy the correct size lumber, the right ogee router bit, the right dovetail blades......they do not exist anymore. Every last piece is fit, shaped and trimmed individually).

This kind of stuff is true craftsmanship, at its' very finest.