Mystery tool damage to bust quarter and half dies?

scubafuel

I posted this to the JRCS email group earlier but heard no theories, so I figured I'd try the boards. Anyone think these marks were caused by the same tool/process?

I was just speaking with LKeigwin recently about the 1809 O108a half. It has a series of "embossed segments" as he notes them on the reverse, caused by something damaging the die during the minting process. Apparently it's unknown what the culprit was, but it's thought to be some sort of tool. The coin is seen here:
1809 O-108a Bust Half

When I saw it, it reminded me of some strange marks on the reverse of the 1806 B7 quarter, seen here:
1806 B-7 Bust Quarter

Both sets of marks have the same basic shape, and radiate in a gentle semicircle. I see particular similarity between the small marks at the base of the eagle's wing on the 1809 half and the marks in the upper stars, just below the clouds on reverse of the 1806 quarter.

The coins were only struck 3 years apart, and so presumably whatever damaged the quarter die was still part of the minting process when the half was produced. Does anyone have a guess as to what made these marks? Are there any other coins with these "embossed segments"? Or is this just coincidental and similar marking, with different causes?

It would make for a great JRCS article if someone figured it out.

Photo credits to LKeigwin.

Matt (scubafuel)

CaptHenway

On the half, are you talking about the radiant lines to the right of the right (viewer's right) wing under ERICA? Those look like clash marks from the denticles of a dropped obverse die.

CaptHenway

Can't tell on the quarter.

scubafuel

Here's a closer look at the quarter reverse. I'm looking at the marks just above the top row of stars and just under the clouds:

I suppose they could be dentils. On the half though, it seems like there are two rows of them. So that would mean it was dropped twice?

CaptHenway

On the half, if the upper, obverse die slipped down in the die holder and was sitting at an angle, the guys swinging the arms of the screw press might have cycled the press back and forth twice causing two sets of clash marks before somebody could holler "STOP!"

The quarter almost looks as if that region were die struck with the planchet off-center in the press, and then stuck back in the press properly and struck. We have seen bust halves in this forum that were misstruck like this and then "corrected."

scubafuel

I can see your point with the half dies. They were probably moving fast enough to make multiple impressions in error.

For the quarter as well as the half, these markings are indicative of the die variety, and are on each coin from that die pairing. I know for the quarter at least, this was the only pairing with that reverse die.

CaptHenway

If it is on multiple coins from this quarter reverse, then it is probably a denticle clash.