Just looked into this thread again. I just opened my desk, pulled out a ziplock bag I dump my change in at work and took a look. The oldest mint red original Lincoln's in the bag are: (1) 1986; (2) 1995; and RATS! (1) 1970-D that is almost totally red. The coins are all at least MS-64+ Now, I have a sealed box at home and several plastic jugs (saving to look for 69-S DDO so I can get a new Porsche) all airtight. I'll guarantee there are some Red cents from the 60's. Further Proof: Go to your local coin show and look inside some of those blue Whitman folders for sale that no one wants. You'll find red Lincolns. I often buy them if there is a degree of color I don't have in the Red Unc to corroded black "color set" I've been working on for years. Fun & cheap hobby. No nit picks about this...there is air in the bag, it gets opened almost every day, and I don't even try to purge it. Now I got to dump this stuff back and get to work.
I suspect that would tone your microwave a lot faster than it would tone the coin. Yeah, and with a mean surface temperature of -160 C or so, I don't think even pure copper would tone very fast there.