Here is the collar halfway off the coat. The old center-back seam allowance is visible, and the collar lining is free to shorten the collar to match the coat seams.
After the seams are pressed open, the collar lining pieces get trimmed and everything is overcast back in place. Over to the side seams.
The underlying waistcoat seams helped line up where the coat seam should be. All the material is removed from the back. With the skirt linings turned back, the canvas reinforcing panel is pinned back in place.
The folded pleats will hang from this, and it holds the hip button cord. An equal amount of material is removed from the back pleat edge to match the side seam.
Behold: the glory of the inside of a mid-18th century British-style regimental coat. Leather cord holds the buttons, and the half lining is apparent. More hemp canvas stabilizes the shape.
All the tack stitching is cut off the pleats and they are ironed flat. Next: the torture of refolding.