This may be a rookie question, but we all have to start somewhere. I have a turn of the last century guitar which is a little beaten up and has been badly repaired in the past. It has been well loved and well played but who ever mended the splits in the body and replaced the nut did it no favours at all. While IMO it is entirely rescue-able I have this to ask. The replacement nut is plastic, I intend to fit a bone one, was fitted using pva which soaked a piece of green felt which butts up to the nut and then extends about 12mm toward the head. I've removed this, so do I need to replace it and what function did it serve?
This isn't it but the construction is very similar. Sorry about the fractured nature of this post.
I'm guessing the felt was to dampen the strings, but mechanically I don't see how it would work.
We see user-applied stuff like that all the time, indeed, usually for the purpose of damping. Sometimes, put in place by a player who was inexperienced enough not to know exactly what was going on in that area. And, often enough, it makes sense, and does its job. Maybe the steel strings rubbed on the pegged slots, maybe the nut was low, maybe it was part of a strap installation, or "protection" for the cord of a strap, maybe, maybe. . .
Could be an attempt to mute an odd-order harmonic above the nut... .