1867 O (Oaxaca) 8 Reales

Adjustments were made before not after the strike. So eliminate adjustment as a cause of the edge weakness.

The coin has weakness at the extremities. The centers are very well struck up on both faces indicating full pressure (note the centering points on the cap and extremely clear breast feathers) - it is the edges where pressure did not develop adequately to fill the dies. The hill the cactus stand on lacks central detail becuase of lack of infill. So how can that happen?

There are two likely causes, improper grinding of the die camber or improper upsetting of the rim.

In the case of improperly cambered dies the distance between the dies when they impact the planchet vary. If the centers are too close only the center detail shows fully - if the edges are too close the edges will be strong and the center weak. This is not a really common situation but in some cases it is the only theory that makes any sense. I use it as a last resort because a failure to upset the edge properly is much more common.

The strike pressures are highest at the center of the die faces and pressure drops toward the edges. This loss of pressure is caused by no retaining collar. Metal flow goes in the direction of least resistance - outward between the dies and not up or down to fill the dies.

The fact that the edge of the planchet is upset by the addition of the design. This is the normal reason edge details come out well at all.

To determine if edging is the cause of the perimeter weakness I checked the edge design. It is very weakly impressed. This would lead to very little upsetting of the edge.

This leaves the edge weakness as most likely attributable to the edge being poorly applied. I once owned a MS 63 1860 Oaxaca that had equally weak perimeters and virtually no edge design at all.

The striations that appear clearly on the unstruck portion of the hill and water are in fact features that were present on the planchet BEFORE the coin was struck. There is no doubt there at all because the area shows no real wear. A much fainter impression survives in some struck areas (like the edge of the hill where it meets the field. That sloping surface seems to retain at least some of the stria.

These stria could be from the rolling, lapping or adjustment phase of the creation of the blank. Not many folks even recognize that these marks actually represent the originl surface of the planchet let alone make the attempt to differentiate the root cause.

In my opinion - the majority should be simple adjustment marks. They are there because the adjusters filed the face of the blank to reduce weight. The reason is simple. Most are cut INTO the blank. In the laminating step the silver bar is drawn through a rectangular die to smooth the surfaces of the strip. Die damage would be in the form of nicks in the die which would produce RAISED stria not incuse stria on the silver strip. A nick with a "tail" would for a brief time create a double line part raised part incuse but these tails should wear off quickly because they would be very weak.

The rolling phase should not really leave long parallel lines on the strip - because the rollers act perpendicularly to the axis of the strip. I could see raised or incuse bumps or both but not long sctatches on the rollers.

So I think in most cases stria that are ALL incuse are due to adjustment and stria that are raised are due to lamination.