The sash had a broken pane which was covered over with plywood and the other pane was painted over. Very strange.
Sash removed
View of the frame with broken bits of glass all around.
The sash is freed
Back side, with wooden board across the width
Sash removed
Plywood is gone.
Robertson screws were used
Time to boil this paint-caked hardware to clean it up.
Glass removed and paint stripping began.
Strangely, the center muntin isn't jointed into the sash. It was just kind of there, and held in with 2 or 3 little nails that were really rusted which was causing the wood to get eaten away. I attempted to glue the muntin in place, but couldn't clamp tight enough, I had to settle for the nail method again since I'm not really that handy when it comes to joinery - I used galvanized nails and filled the gaps with glazing putty.
Time to clean up those hinges, removing the screws from the sash side was exceedingly difficult due to all the paint buildup, the white paint went easier.
Back side
I ended up replacing both panes of glass, I found that the painted pane actually had a missing chunk and they had gone overboard with glazing putty to patch, so I just replaced both panes. The pane was also exceptionally thick, something like 3/8 glass.
Window reinstalled, the lacquer got chipped up during reinstallation, so I had to touch it up afterward.
Sash reinstalled!
A few months later when the weather was warm enough to paint the sash frame, looks great now! Much better than everything being painted taupe like before!