NGC insert volatility

[marvf]

I have been told by a very reliable source that years ago, when cracking out NGC coins from their slabs, a very strong and disagreeable odor was noticed coming from the slab insert. This apparently came from the slab insert. Both the original black insert and the immediate successor white insert exhibited this problem. When PCGS (who were doing the crackout in connection with cross-overs) questioned NGC about this issue, they were informed that, although the insert was "inert," it wasn't 100% inert (??). Thereafter, NGC changed the insert material and the problem went away. This change was made probably around 1991.

 

I am concerned that this plastic insert material is in some of my slabs and may, over the long term, have a deleterious effect on my coins. That's why I would like be able to find out a method to determine the approximate age of the slabs that I have. One of my expensive English coins was in a slab by 1999, and was not in a slab when it appeared in the Willis auction of 1991. So I don't know just when it was slabbed, but I understand that there is a book out that goes into the subject of the various generations of slabs and the characteristics of each of these generations. Can someone help me find this book? Alternatively, will NGC provide the slab date for coins I own?

 

Does NGC care to comment about this insert volatility issue? The source is a very reputable former insider at PCGS.

 

Thank you.