1971 us quarter groove around edge of coin, not rim

kava

hi, i have a 1971 quarter that CoinStar would not accept. It has a horizontal groove going around the middle of the edge of the coin, not the rim. it goes all around the coin perfectly. you can still feel and see the vertical lines, notches on the edge. i would say the groove is about a 32nd of an inch in height and a 64th of an inch in depth. it is hard for me to decribe it. looks kind of like a sandwich but isn't. has anyone ever heard of this type of error in a coin before? who can give me more info on this type of coin?
thanks kava

Julian

The mark is probably from a counting machine.

PerryHall

Sometimes acid will eat away the copper core but not attack the copper-nickel alloy cladding leaving a groove around the edge.

cladking

Welcome aboard.

If the groove is smooth then I'd guess it's machined.

There are some possibilities of it being a legitimate error but it's unlikely. You'll probably
get some of the error experts to post if you can provide a picture or a good scan.

kava

this is the thing the edge of the groove is not smooth, it is not like acid ate at it either, the groove still has all of the ridges still in it where they are supposed to be. the ridges in the groove are lined up with the rest of the ridges on the edge. this is the best way i can describe it. i really believe the error on this coin was made this way when the coin was struck. when i wrote notches i meant the ridges. i never heard of a counting machine creating this type of groove. so i really don't believe that happened. if it was attacked by acid wouldn't it be rough? wouldn't the ridges be smooth then? here i am attaching a scan of the edge of the quarter.

Conder101

Yep, soaked in acid. The acid eats at the copper evenly so the reeds are retained even as the diameter of the copper center is reduced. Think about this, the reeds are formed by the metal being forced against the collar. So for the copper to have the reeds on it, it would have had to have been out at the same diameter as the clad layers at the time of striking.

kava

what are reeds? is that what im calling ridges? are reeds part of the striking process that forms the ridges? i don't know what you mean by the last sentence.

So for the copper to have the reeds on it, it would have had to have been out at the same diameter as the clad layers at the time of striking.

are you saying that you think the coin was struck correctly and then later was in acid? that is why the ridges or reeds are showing still? are they called reeds on the edge?

were you able to see it in the scanned photo?

kava

cladking

The ridges are called reeds and are formed by the "third die" when the coin is struck.

The obverse and reverse dies will exert so much pressure on the metal that it will be
squeezed out in all directions unless there is something to restrain it. This is the function
of the collar in which the coin is struck.

A coin struck out side of the collar is called a broadstrike and will be larger than a normal
coin. Reeding on a coin is evidence that it was struck in the collar and if it is present then
all parts of it had to have hit this "die". There is some variation in how it hits the collar or
in the condition of the collar but these are freaks and would not normally result in a groove.

Acid doesn't merely remove metal from the copper core at an even rate from the surfaces of
reeding. If it did then the reeding would very rapidly disappear since these "ridges" would
be getting attacked from both sides. The metal varies in hardness and the acid eats the
softer metal first which preserves the appearance of the reeding for a surprisingly long time.

kava

Hmm I learn something new everyday. Ok then, so the CoinStar spit out the quarter because of the weight of the coin? Not the size? Is that how they count coins? So if some of the copper was missing (because of the acid) then the coin would be lighter. I also never knew what obverse and reverse meant. That has to do with the "third die"? How can I tell the difference (between obverse and reverse) when looking at other coins?
Thanks Kava

Conder101

The obverse of a coin is usually the side with the head or portrait. This doesn't always work, but it holds true over 80% of the time.

Modern coins can be looked at as having been formed using three dies. The obverse or heads die, the reverse or tails die, and the collar die which creates either the plain or reeded edge of the coin.

Coin operated machines can perform several tests on a coin to tell if it is good. Checking the weight and diameter are the simplest.