concave surfaces

DanArgent

I have noticed that on most coins the background on the obverse is usualy a bit concave. Some coins are more than others. Is a higher degree of concavity desirable or not?

I also noticed that is is common for the image on the coin to be off center. Is this desirable or not?

Dan

Shamika

Concavity gives better depth of field to whomevers large bulbous head is on the oberse.

cladking

Most coins have a concave and a convex side to improve stiking characteristics. This
can have a dramatic affect on how the coins look as they wear since the concave side
will wear inward from the rim and the convex side will wear outward from the center.
The older Washington clad quarter had the large relatively smooth portrait of Washing-
ton to take the blunt of the wear on the convex obverse and the edge lettering and
rim to take it on the concave reverse. The concavity was reversed in '96 though.

This shape also determines their path through the air so on pre '96 issues it's better
to call tails and on the later ones, heads.

DanArgent

are you serious about the coin fliping thing or was that just a joke?

My question was more about the degree of concavity. If I have two ms-60 quarters and one is more concave than the other which is more valuable?

Dan

Shamika

I would prefer the coin with greater concavity. Looks better.

cladking

<< <i>are you serious about the coin fliping thing or was that just a joke? >>



About half serious. A coin is likely to change sides one or more times after it's dropped.
If it doesn't then it's a lttle more likely to end up concave side up which means tails.



<< <i>

My question was more about the degree of concavity. If I have two ms-60 quarters and one is more concave than the other which is more valuable?

Dan >>



In the series I'm familiar with there is little variability in concavity within a date. There
may be slight diffferences in die preparation or strike characteristics but the aim for all
the coins is identical. Certainly specialists would be interested in this since it would con-
stitute a die variety, but you'd have to find the interested collector.

What coins are they?

Scioto

"What coins are they?"

Jefferson Nickels?

Conder101

One reason for the concavity is that it makes the dies slightly convex. This makes the dies a little easier to polish, and causes the dies to come together in the center first and as the pressure increases there the planchet metal flows out radially from the center. The convex dies as they continue to come together encourage this flow and it facilitates the filling of the outer voids in the die.