It is very common to hear a coin described as having "iridescent toning." But what is iridescent toning? The commonly accepted definition involves lustrous toning in which the color pattern changes with the viewing angle of the coin. But for those that have never seen an iridescent toned coin, they might not understand what that means. The following photographs of a 1942-S Jefferson Nickel PCGS MS67 should provide an excellent example or iridescent toning. Heritage Photo Note that the coin has what I have referred to in the past as quintessential war nickel toning. The area of cobalt blue and emerald green is iridescent. And although it is very clear and powerful when the coin is viewed straight on, the colors change drastically when turned into the light as can be seen in the following photo. My Photo When viewing the same areas, the toning is now decidedly pink and yellow. The change in appearance is so drastic that at first glance, most people viewing both photos side by side would think they are different coins. The tell tale die crack and planchet flaw on Jefferson's cheek confirm that they are indeed the same. Heritage Coins defines iridescent toning as "Probably the most desirable form of toning on a silver or nickel coin. Iridescent toning covers virtually all of the coin's surface, while still permitting all of the coin's natural lustre to shine through with its full intensity." Because rainbow toning can often impede the luster of the coin, iridescent toned examples will often bring large premiums in price. It does not matter what the color scheme is on a toned coin, without the luster to give the coin that "pop", the coin will not have the eye appeal needed to drive a strong premium. However, the astute collector should always be wary of those sellers offering iridescent toned coins. Iridescent coins are not always attractive at every angle and often times the seller's photo will show the absolute best angle which may be elusive to even see in hand. So you may think you are buying this: but receive this: Look closely, they are the same coin. Iridescent toning can be extremely beautiful but purchasing these coins is wrought with danger. By all means seek out these coins, but be very wary before pulling the trigger to buy.