Explain DMPL

lablover

How does a coin aquire the DMPL qualities. I've heard it's because the coin was one of the first ones struck. And, therefore, gain a proof like quality. Is this correct.

Cam40

I think it has more to do with the way the dies are made.But dont quote me on that.Unless I,m right ofcourse.

littlewicher

PCGS currently only applies it to Morgan Dollars, I think. PL has to have mirrors, not sure how much, though. DMPL has even more mirrors then the PL, plus I think there has to be contrast. I'm not an expert or anything.

nwcs

A DMPL is quite simply the finish on a coin that was one of the first strikes from a die that has been highly polished. The designation only refers to Morgans right now, but there are other coins with a similar surface. If I recall right, only about 50-100 strikes from a very well polished die are DMPL, then it transitions into PL and then into frosty luster (from die erosion). Of course, things can interfere. For example, after a day's work, the dies are put up. The next day they may not match the same set of dies for striking new coins. SO you can have a PL on one side and frosty on the other. And when a die gets to being frosty, they can be polished back up to being prooflike.

littlewicher

NGC is starting to designate all coins PL and DMPL for those that apply. I think that's kind of cool.

Cam40

here lilwicher have some kool-aid.

lablover

Thanks to all for the reply's. It's a bit more clear now.
LabLover

FC57Coins

A couple of things need to happen for a coin to get a DMPL finish. In the case of the Morgan Dollar above, the process starts with the rolling of the metal into the strips from which the blanks were stamped out. When the strips are made, they are passed through rollers back and forth until the strip reaches the proper thickness. In some cases, when the rollers were particularly smooth (new) they tended to give the strips a mirror-like finish. In addition, back in the days when these dollars were made, the die faces were ground down to a mirror finish on a slow rotating diamond dust wheel. When these dies were used, they also helped impart a mirror-like finish to the first few coins that were made from the fresh dies.

Frank

Cam40

what Frank said.

lablover

What did he say? I got confused.
No, just kidding. Thanks Frank.

Macqui

Frank-

Great explanation, it couldn't be said better. Those DMPL's sure are pretty.



Macqui

GC's DMPL Morgans

Conder101

Ok let's just stick with the Morgans. When the dies are made one of the last steps in their production is the hardening process where they are heated o a high temperature and then suddenly quenched. naturally during this heating process an oxide layer is created on the face of the die that needs to be removed before use. That is accomplished by polishing the die face with the diamond lap and it can result in a partial of full mirror finish on the fields of the die depending on now extensive the polishing is and the fineness of the abrasive on the lap. Furthermore once the dies would be received at the various mints they were often submitted to further grinding or polishing in order to impart a certain curcature to the face of the die. This curvature was needed to help with the striking of the coins inorder to bring the design up fully. Since the different mints tended to have presses of different manufacturers each mint had to do it's own grinding to match the peculiar needs of their own presses.

The polished fields of the dies would in turn impart the coins with the same mirror-like qualities. The reflectiveness of the fields on the coins being directlive related to the extent of the polishing the die had received and again the fineness of the grit used. This refeltivness is measured by the distance at which text can be read in the reflection. If it is 1 to 2 inches it is a semi-prooflike, 2-4 is prooflike, 4-8 inches is DMPL, and over 8 is UltraDMPL. (I may be off on those exact inch measurments.) Contrary to common belief the PL rating has nothing to do with the amount of cameo contrast between the fields and the devices.

The highly polished fields of the dies are rather fragile and after just a few strikes the abrasive movement of the coinage metal across the field creates microscopic flowlines in the die metal that begins to reduce the mirrors and within a few hundred strikes the PL qualities are gone.

During the dies life sometimes the die will be removed and repolished to remove minor damage such as clashmarks. If this occurs then the die may again produce PL or semi-PL coins again for awhile.

This process occurs with all dies but there were so many more dies needed to create the dollars and so many more have survived to today that the relativel much larger numbers of PL quality coins in the dollars draws our atention to them and the PL coins in the other denominations are neglected. Another reason why the dollars had more PL coins was because they need more work on establishing the field curvature. The curvature on the smaller denominations was not as critical since the presses easily had the power to strike them up fully no matter what the curvature was. The size of the dollar coin though meant that every means to ease the striking needed to be employed.

Rittenhouse

conder has it basically right. Just 2 points:

1. Since the hardening process results in the die being very hard but brittle, the die needs to be tempered by heating to a straw or blue color and allowing to air cool.

2. The basining of a die (curvature) is just as critical for small dies. The curvature affects strike, wear, release from die, etc.

See the 1896 & 1901 Mint reports for an excellent discussion of the die making process written by Charles Barber.

lablover

Thanks again all...but, you've made my head hurt. Not sure I'm capable of absorbing this much knowledge. You guy's are impressive!!!

Gilbert

lablover,

For simplicity sake, go with Frank's description, although teh "die-making" process is quite informative.

BTW, Morgan dollar dies typically received more attention (basining, re-polishing) than other denominations. Notice how much different in appearance Peace dollars are than Morgan dollars. Mint personnel DID NOT spend as much time "maintaining" the dies as they did with Morgans. That is one reason one rarely, if ever, see proof-like Peace dollars.