Greetings, hoping someone with good knowledge of Gibson PUPs might help me out. I have a pair of what are commonly referred to as Tar Backs, factory PAF's which have the covers sealed on with a black silicone like substance. Each of them measure in the 5.5k range, which seems pretty weak. If anyone can help with any of the following it would be much appreciated: What years were these used, in what models? This have gold covers. Is the 5.5 considered defective. Seems weird both are the same? Assuming they were >7k new, what might have degraded them? Is there a way to unseal these and get the covers off? Heat gun and patience? Thanks in advance for any info.