Yes, TxAg, marked coins could be used - but most marks are sharpie type marks and could be washed off. I think the ring scratches are more permanent and useful. The biggest problem is that the object of interest is constantly being removed, so a population estimate would require making assumptions that are untested. I'm leaning more toward a matrix of factors - marks, ring scratches, and skunks in a weird way to remove emotion from the decision.
But, Just as you discovered, something changes with the boxes and all of a sudden, things look brighter. I've had one good box since a Brinks box with my Wender, so 20 skunk boxes out of 21. I decided to drive a bit further away today to pick up 3 boxes of Loomis haves. I just now finished the first 2 boxes and these are about the best boxes I've searched. First box had 30 silver, of which 3 were walkers, 3 Franklins, 4 1964, and 20 40%ers. Second box had 26 silvers, including 1 Walker, 2 Franklins, 7 1964, and 16 40%ers. I've still got a box to go and all I know is there is one ender (couldn't help it - had to look). So now I'm happy and considering reducing my Brinks boxes from 3 to 2 or 1 and continuing with the Loomis boxes, even though it means 65 miles round-trip rather than just 8. On the way home, there was a multiple car accident that included several wrecked police cars. I haven't seen so many wrecked police cars since watching "The Blues Brothers".