I picked up what was sold as a 1974 original P Bass and took it apart to take a closer look. I found the shim and calling card of who I assume installed it. Not munch information was available from the guy who sold it to me, but, just like every loved one - I'd like to know as much about the history and reasoning behind the shim as possible. I need to take it to my tech for a once over and would like to provide historical info about the shim since it will factor in, one way or another. Any ideas? Richard C...??? Thanks in advance!