Mitch Spivack: In 1993, the U.S. Mint produced a set of coins known as the “Philadelphia Set”. The set contains a special silver Bicentennial medal only found in this set (and struck to recognize the 200th anniversary of the striking of the first official regular issue U.S. coins produced for general circulation by the Philadelphia Mint; namely the large cent struck in March, 1793), a 1993 $1 Proof Silver Eagle and a $5, $10, and $25 Proof Gold Eagle (the set did not contain the $50 Proof Gold Eagle which explains, in part, why the mintages are higher on the fractional proof gold coins for this year). For the first time since the start of the Eagle program, the three gold fractional coins, as well as the Silver Eagle, were minted in Philadelphia and bear the “P” mint mark. The coins are housed in a special U.S. Mint presentation box –each coin placed into a single heavy green piece of cardboard contained within the set. It has now been about (16) years since the time these coins have been placed into this green cardboard by the U.S. Mint and the proof silver eagle has reacted to its “environment”. In fresh, original, sets, the proof silver eagle has now often turned a lovely shade of purple around its rims (and extending slightly into the coins surfaces) in a color pattern unique to the “Philly Set”. I have seen a number of these coins already with more advanced toning where the myriad shades of purple have extended well into the coins’ surfaces, beyond the rim, creating simply a stunning toned specimen. Interestingly, the silver medal, which is only 90% silver and 10% copper (as opposed to the silver eagle was is 99.9% silver) is not toning yet anywhere close to the degree the silver eagle has naturally toned in these sets in the same environment. If you are a toning enthusiast, as I am, be on the lookout for this very special naturally toned proof Silver Eagle!