I was thinking the other day of a possible way of estimating the silver content per sheet, but of course there are a lot of variables and technical expertise that I don't have so I'm not sure how accurate it would be.

First, thickness of the tracings would have to be determined. This is one of the problems because an average would have to be used most likely.
Second, place the mylars into a scanner and export into a graphics or other type of program to determine the area of the tracings some how. This ends up with problems such as tracings on both sides running across each other, and also non-transparent mylars.

This is just an idea I had, but thought it could maybe turn into something useful.