Question on Gram weights

[Dozer D]

Has anyone every taken notice on the discrepancy of weight measurements, of say the DIME for example.
A typical AG Rosie is 2.50 total grams., if you take 90% as the silver content =2.25grams (or) .079364 oz of silver.
The all the books(RedBook) states that the AG Rosie has .07234 oz of silver content.

.079364 oz (OR) .07234 oz. what is correct. Am I missing something here?
Can someone explain the difference.

 

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[Avago]

Red book is listing TROY ounces which is different from ounces. Check out U.S. Silver Dime Melt Value Calculator and you'll see the silver content measured in both ounces and troy ounces. One ounce is equal to 0.91146 troy ounces.

 

[TheMastermind]

What Avago said.

1 avoirdupois oz = 28.35 grams.

1 troy oz = 31.1034768 grams.