This Baldwin piano has a large one piece lid, and a drop action. There is virtually no place for a mute strip and no way to get the Papps mute under the hammer heads.
The only way to easily tune the treble of this piano is to use Double String Unison (DSU) technique, or dismantle the piano lid. Even then, getting under the low hammer heads will be a problem. 
With DSU, you can insert the mute from above, it does not need to be out of the way because the mute only mutes the outside string, and of course there are all the other benefits of the technique. 
Like the added benefit of being able to tune bichords with no mutes at all! 
Contact me if you want to know more about Double String Unison tuning.
