I have a '74 Precision I bought new. I just noticed a black, tar-like substance oozing from under the pickguard. The location is under the strings. After removing the pickguard I see it goes from the bottom of the pickguard to the bottom of the bridge pickup (about 1 inch), although I doubt that the pickup has anything to do with it. Does anyone know what this is or have you seen this on your bass? Could this be heat related? How would I best clean this off without marring the finish? thanks.