VAM stands for Van Allen and Mallis, the authors of the reference that catalogued Morgan and Peace dollar die marriages and gave each one a number. An attribution reads date-mintmark VAM-number — “1888-O VAM-4” — and it identifies a specific pair of dies, not a grade, a condition or a value.
The catalog is large enough that specialists work from curated subsets: the famous “Top 100” and “Hot 50” lists exist precisely because several hundred numbers is too many to shop from. The attribution corpus is maintained and photographed by the specialist community at VAMworld, which is where you verify a coin before you pay a variety premium.
Two practical warnings. First, VAM numbers are revised as attributions are refined — a number is a pointer into a living catalog, not a permanent serial. Second, and separately, a grading service has to recognise a variety before it can be bought and sold as one. The varieties below are recognised by PCGS with their own catalog numbers, which is what gives them a market rather than only a name.
Die states — the second axis
A die changes while it works. It clashes against the opposing die, it cracks, it gets gouged, and it is polished back into service — each time removing a little detail. The same variety therefore exists in an early, middle and late die state, and the diagnostic you are looking for may be bold, faint or polished away entirely depending on where in that life your coin was struck.
This is why two coins of the same VAM can look meaningfully different — and why die-state specialists collect the sequence rather than the single coin.