Now to the tough terms: Wire edge, wire rim and knife rim.
RogerB
Posts: 8,852 ✭✭✭✭✭
Wire edge.
Wire rim.
Knife rim.
Three oft-misunderstood and confused terms date from the 19th and early 20th centuries. Over the decades, nothing has been done to improve understanding or accuracy. It might take just as long to change old habits.
First, let’s be clear about “edge,” “rim,” and “wire.” As all here already know:
The “edge” is the thickness of a coin also called its third side. It may be plain, reeded, lettered, ornamented or otherwise treated.
The “rim” is a raised area around the periphery of the design. This serves to protect the design from abrasion and to support the coin for stacking. A coin’s rim is usually plain and flat on the upper surface and its width may vary from nearly zero to a noticeable percent of the coin’s diameter, depending on face design and die shape.
A “wire” is commonly defined as metal drawn out into the form of a thin flexible thread or rod usually of cylindrical cross section.
Wire edge.
On U.S. coins, a coin edge has had various ornamental and security treatments. But, no coin has ever had a raised or incuse “wire” anyplace on the edge. Several tests were made in the 19th century but no coins resulted. (Some foreign coins have an incuse wire shape at the mid-thickness of the edge.) Thus, “wire edge” is meaningless in relation to U.S. coinage. This should be abandoned in entirety.
Wire rim.
This is an “oldie” but not a “goodie.” The term is tossed about with all sorts of meanings depending on who is talking and the coin(s) under discussion. The most common hobby use is as a synonym for a “fin” which is a thin flange of metal raised above the rim at the extreme periphery of a coin. It is, and has always been classified by U.S. Mints, a manufacturing defect.
This “fin” does not resemble a piece of thin wire. Rather it is a very thin, irregular extension of metal. This is caused by a mismatch between die faces and the collar. It does not indicate the force used to strike the coin. (A very good coinage example are MCMVII double eagles. The first issues were marred by a prominent fin on nearly every coin, but when corrections were made in mid-December nearly all of the fin was avoided.) A better term exists and should be used.
Fortunately, several prominent TPGs and authors have adopted “fin” as the correct description of this defect.
Knife rim.
This little term is commonly defined in numismatic glossaries as being a synonym for “wire rim.” But of what use is a term that is a synonym for a meaningless expression? The most frequent use of “knife rim” was by Breen in describing the absence of a rim on the Saint-Gaudens $10 coins of the first designs. But it was also used by him in describing a fin or a “wire rim” and by others for various imagined conditions.
Here’s what might work better. Use “knife rim” only when the field curves or meets the edge directly with no defined rim. That is, the place of a rim is taken by a sharp edge, similar to that of a knife. It’s not a perfect description, but avoids confusion. Suggestion - modify definition so it is specific to only one observed situation.
OK. Have fun. 
PS: When you check Numismedia's glossary for "knife rim," note that the comment about 500 eagles being patterns is wrong. They were made as regular issue coins just as were the first 500 MCMVII double eagles.
Comments
I'll add some photos or members can do so.
Be very careful of that one!
It's not mine.
I don't want to get anywhere near that one.
It's on the net.
Tetanus Rim..
i really feel for lady liberty.
@RogerB....Thanks for the informative explanation of these terms... I think many have used them interchangeably... and I would wager they are on some slab labels as well... Cheers, RickO
Roger states the facts clearly. Whether people will take note of the facts or not remains to be seen.
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As an aside, while I was at ANACS I noticed that three different Proof Morgan dollars of a particular date appeared to have been very finely and carefully filed along the outer periphery of the raised rim in the same area. The workmanship looked the same, and I have wondered if this was done at the Mint to remove "finning," but I do not know.
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TD
The High Relief $20's have been described as wire edge and plain edge. There was no difference; just a matter of some gold getting between the collar and the coin, producing what some call the wire edge. The mint did not design two different rims or edges.
I firmly believe in numismatics as the world's greatest hobby, but recognize that this is a luxury and without collectors, we can all spend/melt our collections/inventories.
eBaystore
RE: "As an aside, while I was at ANACS I noticed that three different Proof Morgan dollars of a particular date appeared to have been very finely and carefully filed along the outer periphery of the raised rim in the same area. The workmanship looked the same, and I have wondered if this was done at the Mint to remove "finning," but I do not know."
Mint documents state two reasons for not liking the fin: it was unattractive and represented poor workmanship, and it was subject to immediate abrasion and resulted in an underweight coin. This was especially a problem on gold. A third reason developed as the scope and sophistication of vending machines increased. A fin often made a coin too thick to roll through the mechanism, resulting in loss of the coin and jamming of the device.