1978 JFK Wide Collar? Mad? What Is It?

With regard to tolerances, the US Mint only discusses having no tolerance for discrimination! There is no reference to diameter tolerance. One source (cited below) which discusses Weight Tolerance but lists none for diameter. Am I to infer that there is zero tolerance for diameter? The Mint says diameter is 30.61 mm, other sources mostly round off to 30.6 mm.

Here is the other source:
http://coins.about.com/library/US-C...in-Specs.htm

"With regard to tolerances, the US Mint only discusses having no tolerance for discrimination! There is no reference to diameter tolerance. One source (cited below) which discusses Weight Tolerance but lists none for diameter. Am I to infer that there is zero tolerance for diameter? The Mint says diameter is 30.61 mm, other sources mostly round off to 30.6 mm."

I'm sure there is a tolerance for diameter. The key is finding what it is. About three years ago as part of the Summer Seminar I went on the inside tour of the Denver Mint. They were minting nickels that day. I noticed each press had a paper taped onto it with inspection numbers. They were inspecting three things. First was weight, then diameter and then thickness. There was an upper and lower limit for each one. The fact that they inspect the thickness to a tolerance was what caught my eye the most. But there are tolerances to all of these dimensions.

"To me that looks like counting/rolling machine damage. I have never seen that have such an impact on the rim. It is like there are 2 rims! That is what I am so confused about!!"

The Rolling Machine Damage has nothing to do with the rim. The rim at the top of the obverse just has some finning which is common.

The diameter of your coin is only .04mm larger then the given diameter for a half dollar. In inches it is only .0015" larger. This is such a small amount that I feel it is well within the tolerance.

This coin appears to be to be a minor Misaligned Die. These often lead to minor collar clashes that wear away at the ID of the collar and the OD of the die. As far as Wide Collars go, no two coins measure exactly alike. In fact, the same coins will measure different if measured from two different locations on the coin. This is due to collar wear and damage which starts right from the start of minting. As such there is a normal variance.

Variations in diameter are most commonly due to worn collars and coins being run through edge inscription machines after they are struck. Broken Collars are also a rare cause. Other causes are almost non-existent but can occur.