1877 Seated Liberty Quarter You Vs NGC (Grade Posted)

I have no idea. I think it is pretty much the whim of the grader. There are many that would find your coin very attractive, and they would pounce on it with it being certified and CACed. The grader and the evaluator at CAC may have thought the same thing. I see the luster, and I think your pictures might be muting it. I will say that the reverse has more luster than on a typical EF-45, and if the obverse is a similar story, that is probably what drove CAC to bean a dipped coin.

Let me get one thing straight. I was not trying to belittle your coin. I think the toning is genuine album toning that is attractive. My toned SLQ looks much worse than yours as far as the surfaces are concerned.

What happens when a coin is dipped is the top layer of silver atoms are stripped from the coin. Usually, this is to remove the silver atoms bonded with sulfur (or sometimes oxygen). The silver atoms bonding to other atoms cause the dark color on circulated coins, and when they are stripped, the silver has a silver color again. This leaves the silver surface raw and highly reactive, so placement into an album with a high sulfur content will induce rainbow album toning. So worn coins with white silver surfaces have been dipped. The way the coin was stored causes toning.

On AU and MS coins, stripping the silver lowers and eventually takes away the microscopic metal flow ridges that are the essence of luster. That is why dipping is generally not recommended for high-grade coins.

However, I think there are some dips (EZest comes to mind) that takes the sulfur from the silver atoms and bonds the sulfur atoms to hydrogen atoms to make H2S. These don't strip off the silver atoms themselves.

I hope I explained everything correctly.

You might be mistaking die scratches for cleaning lines. Die scratches are a common occurrence in early 19th century coinage.

Also, I highly doubt this coin was "dipped". Was it cleaned at some point? Sure, but in all likelihood the OPs coin is an old water and cloth cleaning from a hundred years ago and the coin found its way into a Wayte Raymond cardboard holder where it developed its toning pattern.

This is a typical collectors debate. Buy the coin, not the holder or complimenting sticker.


I would also start with this article for a very detailed explanation of thin film interference.

http://www.jhonecash.com/research/t..._physics.asp

TypeCoin,

Here is a Seated dime in a PCGS holder graded problem free VF30 with strong rainbow toning. Your position is that this circulated dime had to be cleaned or dipped to enable the toning because the dime's original surface in VF30 condition would not tone in rainbow colors without assistance of a dip or cleaning.

If this dime was in AU condition, could it tone in rainbow colors without a dip or cleaning because most of the original surface and luster is still intact?

Thanks for the discussion on this topic. I found the 1861 example to be very interesting, and beneficial to my understanding of toning.

I did some research into the physics of toning on circulated coins to answer your question. I hope what I uncovered is right.

The rainbow toning is caused by thin film interference, which requires a reflective surface underneath the thin film (oxidation) to cause the colors. Without this reflectivity, then the coin would be brown/grey.

While silver coins were circulating, the constant abrasion of human hands kept them from toning, so they all had a dull white look to them. When the coins got pulled out of circulation, they got the chance to tone. Some coins reacted with oxygen to produce a black layer of silver oxide, while others reacted with sulfur to get a rainbow tone. However, as this sulfide layer got deeper, the worn coins did not have the surface reflectivity to cause the pretty colors seen with thin film interference. AU/UNC coins had luster that had enough reflectivity to make the colors pop when light hit them. This phenomenon can be seem in Oih82w8's EF-45 1861 Half Dime, where there is vibrant color where there are remnants of original luster on the reverse. Everything else is grey.



This is also seen on this CBH:





When silver coins are cleaned, the sulfide/oxide layer is made very thin to nonexistant again. The raw silver has a natural reflectivity that will produce colors for relatively thin layers of sulfide. Also, the surface is often made shiny to cause the colors to pop out, such as on my quarter or this CBH (note the hairlines on the fields).

Great research I love reading about thin film interference. when I try to explain it to non-coin lovers, most of the people in my world, I simply say think of the "oil on water effect" as that is the exact phenomena at work.

I'm sorry, I just don't see how all these rainbow toned coins were dipped. Especially in mid AU examples such as the 1847