Interior French Doors - Three?

I live on the second floor (above the parlor) in a Carroll Gardens brownstone. It’s basically three rooms, the room that divides the street-facing room and the middle room (my living room) has a door frame with a 7 panel glass insert above the frame. The hinges are still on, and there are two holes in the top of the frame. I’m trying to figure out what was there before – doors of some kind, with about 30″ panels, it seems. Any suggestions on (A) what was there originally? or (B) how i could put some replacement doors in there? or (C) where to start? Thanks!