This particular book originally had laced on boards. The board were now detached, but were important to keep. Since the original leather was delaminating from the boards, I decided to remove it and attach it to new boards.
I was able to remove the original leather from the boards gently with a spatula. I also removed and kept the turn-ins. I glued down and turned in the new PC4 spine piece, infilled the boards, and glued down the original leather and turn-ins. Where sections of the turn-ins were missing, I glued down PC4 strips. I lined the board edges and missing areas with Japanese tissue. Then glued down the end papers, and toned the tissue to match. This was then end result.