I have a new (to me) G-20, that I recently bought. I believe it is a Gen-3 model. On field strip I have noted no marks on weapon to indicate that it has ever been fired. It does still have the copper "lube" on the slide rails. Is this compound actually lube, or a very fine type of lapping compound? I thought that it was lube, but have been told by a gunsmith's helper that it was polishing compound?? I have read several post on the copper material but have not determined what it actually is?? Thanks in advance..Bill.