Goldfinger, I will try to answer your questions (1) what is a
VAM? Two persons, Leroy Van Allen and George Mallis collaborated together on identifying 'die pairs' used on the Morgan and
Peace dollars. A
VAM is an acronym for Van Allen Mallis. (
VAM) Their collaboration is the definitive compilation known as A Comprehensive Catalog and Encyclopedia of Morgan and
Peace dollars now in it's 4th addition.
You see, the
Morgan dollar was minted from 1878 to 1904 and then for one year in 1921 and the Morgan series has all kinds of varieties.
In 1878, the first Morgans minted had the eagle on the reverse with eight tail feathers showing. Some bird society notified the mint that there were no eagles with eight tail feathers, they only had seven tail feathers. Oops. (2) Are there two different 1878's? Let's continue our discussion.
So the mint rehubbed the eight tail feather dies and these became the 7 over 8 tail feather varieties. This means that some coins had remnants showing under the now seven tail feathers. There are also other distinct features such as very distinct doubling and shifting on the reworked dies. The coin in question is known as a
VAM 38 because certain aspects are different. On the obverse the word L-I-B-E-R-T-Y is strongly doubled across the headband and shows the greatest shift known for any
Morgan dollar. On the reverse, 5 tail feather remnants are showing. Hence, the 7/8 tail feather variety. Now to answer your question, in 1878 you have the eight tail feather variety, the seven over eight varieties (16 varieties) and the seven tail feather varieties. (3) does this apply to all mints or only Philadelphia. For this part of the discussion this concerned only the Philadelphia mint, but varieties are spread across all mints.
The real fun and for another discussion is the reverse used in the first half of 1878, then changed later in the year and that reverse is identified as the reverse of 1879.
Morgan dollars truly offer the collector unparalleled varieties and many of these varieties are quite common and carry no significant premium, but there are others that are considered to be ultra rarities and worth a whole bunch of money.