Morgan Dollars are some of the most beautiful U.S. coins ever made, not only because of their design but because of the quality of the strike on many of the coins, especially the earlier dates in the series. Such Morgan Dollars are called DMPL (Deep Mirror Proof-Like,) Prooflike (PL) and Semi-Prooflike (SPL)
There are a couple of ways to tell the difference between DMPL, PL and SPL Morgan Dollars.
The most common way, and probably the most reliable, is to hold the coin on its edge next to a page of printed matter (such as a newspaper) where you have marked off the inches. You should have good light directed towards the coin (but not directly into the coin such that is reflecting). Then, look into the coin's mirrored surface and see how far down the scale you can clearly read the text.
DMPL Reflectivity Scale
Here is the scale that denotes the proper designation for the coin, based on reflectivity.
- Semi-Prooflike (SPL) - 1 to 2 inches, devices must be frosted
- Prooflike (PL) - 2 to 4 inches of reflectivity
- Deep Mirror Prooflike (DMPL) - More than 4 inches
- Ultra Prooflike (UPL) - At least 8 inches
The designation of Ultra Prooflike is not in widespread use, and qualifying coins are fairly rare. The standard to qualify for UPL varies; some authorities say 12 inches of reflectivity should be the standard.
It is important to remember that in order to qualify for the designations noted above, the entire surface must be mirrored, with no grayish areas or lost reflectivity due to variations in the mirror quality. Normal bag marks and scuffs are permissible. If only one side of the coin is Prooflike, the coin doesn't qualify unless the grading service offers separate designations for each side of the coin, and even then, usually the obverse must be the Prooflike side in order to count.
Another DMPL Testing Method
Another test that can be used to check the reflectivity of a Morgan Dollar is the "finger test". Lay the coin flat on the felt (you don't let your coins touch hard surfaces like tables, do you?). Make sure there is a good source of light directed towards (but not into) the coin, and then hold your index finger above the coin, raising and lowering the finger to determine how far the finger can be moved away without losing sharp definition. Sharp definition is the key here (and why the finger test isn't as reliable as reading text in the mirrored surface). If the finger isn't sharply defined in the coin's field, it's too far away to count. The same scale of inches of reflectivity apply.
Slabbed DMPL Morgan Dollars
The tests above are not as accurate for coins that have been slabbed because the plastic case will slightly diffract and dilute the reflection. It is recommended that you only buy DMPL Morgan Dollars from top tier grading services such as PCGS and NGC, as altered coins and fake frosted devices are a real problem in DMPL Morgans.
Another reason to buy only reputably slabbed coins is that sometimes it takes an expert to tell the difference between a clean DMPL Morgan Dollar and a Proof Morgan Dollar.
Other DMPL Coins
Although the designation DMPL first emerged to describe Morgan Dollars (and later certain Peace Dollars), the term is being expanded now to describe other coins that have the bright, shiny, mirrored surfaces and frosted devices of Proof coins, but which were struck for circulation. In most cases, the dies that struck the DMPL coins were prepared and polished in a similar manner to the Morgan Dollar dies, which included a step called "basining" the dies. Basining was a process that was done to each individual die just before inserting it into the coin press and involved machining the die face to a slight concavity while applying a very fine die polish. Sometimes these basined dies were buffed afterward, resulting in an even deeper mirror. Unfortunately, the mirror effect only lasted for the first few thousand strikes, degrading slowly to the point where the struck coins were no longer even mirror-like enough to be SPL.