VAM refers to different varieties of Morgan and Peace Dollars. The Morgan Dollar is named after its designer, George T. Morgan, who designed the obverse and reverse of the coin. VAM - Are the changes/variations were made by the designer or not ? Why the changes have not been reported for many years before their discovery ? Significant changes - My example:
The VAM 4 is a doubled die, so it wasn't a change made on purpose. Most of the VAM were not, it just didn't matter much to many collectors where the CC mintmark was micro-located or angled, as long as it was in the 'normal area'. Also many repair jobs on dies produced VAMs and if the repaired die failed quickly, it may have been a long time before it was noticed. In the early days of collecting, even the difference between a CC and S wasn't considered other than normal, collecting by mintmarks would come later.
VAM is the abbreviation of the two author's last names who did some of the initial research on Morgan and Peace dollar die marriages. Van Allen and Mallis. VAM numbers are assigned to each Morgan and Peace dollar based on the obverse dies and reverse dies used. Therefore all Morgans and Peace dollars are VAM's. Some VAMs are just worth more than others based on the type of variety, scarcity and desirability. For example, the 1888O Hot Lips is a very desirable variety that is fairly scarce. Lower grades are more common than higher grades. There have only been a few of these VAMs certified as Mint State. For example if Obv Die 1 was paired with Rev Die 1, this may be called VAM1 for a particular year. If Obv Die 1 was paired with Rev Die 2, this may be called VAM2 for this particular year. But this is oversimplified as these researchers don't know exactly what dies were used and when, but over years and years of research much of these mysteries have been put together like a jigsaw puzzle and VAM numbers have been assigned. Some years saw many, many dies used and others only used a handful of dies. But it gives you an idea on how VAM numbers are assigned and this is the point that I am trying to make.
That's the answer to your question Cmcart. Varieties (VAMs) can be caused by many things, tool marks, die clashes, doubled dies, RPMs, RPDs, etc etc, but they are almost always an accident.