JOHNMAN Hello

The basic issue with the 1907 S Peso is that there are a ton of fakes on the market and that caution should always be exercised when dealing with any coin that was test cut on the rim or tested with acid.
I believe the coin is a modern counterfeit. That is my own considered opinion and you of course are entitled to believe as you will.
There is however, one statement you made that you might want to address a bit more closely.
Quote:
The wear accounts for the small loss of weight.
The loss of weight in this case is 0.32 grams from normal. This is a loss of 1.6% of total weight and that is not small. I would expect the coin to be considerably heavier because the wear loss here due to abrasion effects should be less than half of what is reported.
Loss of weight due to wear was a key reason why counterfeiters made most of their coins appear to be worn. They knew and still know that the average person has not done weight to wear studies to determine actual losses. When presented with a worn coin the average person will believe that a lower weight is acceptable. In that way a slightly thickened debased coin that looked worn could be passed off as silver. See for reference:
Money and the Mechanism of Exchange (New York: D. Appleton and Co. 1876) by William Stanley Jevons.
In the days when silver and gold coins were of INTRINSIC value and not mere tokens (fiat value) the acceptable limits of loss were rather small. That is why coin relief is always very low. When a coin wears to About Good (total rim loss on a collared strike) it was no longer acceptable as circulating money. For dollar sized silver coins retirement (or devaluation by actual weight) occurred with as little as a 2.5% loss of weight. Average actual wear observed at the mint for incoming worn silver dollar coins was only 3.1%.
Three Cents mattered.
The coin here is NOT about 1/2 way to AG - far from it.
I recognize that this coin was made after intrinsic value had been replaced by fiat value but the wear standards for retirement based on appearance were not altered for silver coins when the coins ceased to be intrinsic items.
Gold coins were
far more sensitive to the effects of abrasion loss. That is why gold worn to AG levels is rather rare.