Looks like someone was trying to dampen the twang!
I don't see how that could have happened at the factory though. Where did you get it?
God rest ye jelly mental men
I purchased S/h but the screws and all the fittings look perfectly original. Even if it had been apart, and it is highly unlikely, who on earth would stuff a plastic bag inside.
Could the spring have had a plastic bag fitted at the factory that made the springs? To protect it and Diana employed a new guy and he left the bag on it?
We got springs in the compressor place I worked at and some had a plastic bag on them as they were covered in a grease coating. Was to protect it or stop the grease going on the other parts of the boxes contents.