I have this someplace in my files.... The mint made a pile of 20 new coins, measured the height, then divided by 20. The standard silver dollar was not included on the original list quoted in Renaissance of American Coinage 1905-1908.
The mint average was 2.826mm (per Charles Barber - 1900). But, the letter does not say how many times that made the measurement or how the coins were mixed and if they were only from the Philadelphia mint.
I just measured some mixed date/mint BU rolls and got between 2.80 and 2.87 over 20 measurements of differing piles of 20 Morgans.
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I just measured some mixed date/mint BU rolls and got between 2.80 and 2.87 over 20 measurements of differing piles of 20 Morgans.