Seven silver coins in a $500 box of half dollars is a hit rate of 0.7% (not 0.07%). Because there was a gradient of silver coins in the rolls I removed from different sides of that box, I argued that only half of the rolls in that box contained coins from a cache someone brought to a bank. If I am correct, the hit rate would have been 1.4% if all of the rolls had that origin.
On December 20th, I described results from a box I acquired at the same bank that contained 34 40% silver Kennedy coins and two 90% silver half dollars (a 3.6% hit rate). If my cache interpretation is correct, 2.5% of the half dollars in Loomis rolls that incorporate that cache are silver. Any CRH would be happy to find 25 silver half dollars in a box (including three 90% silver coins). That's why I asked the bank manager to order five more boxes from the same site. Keeping my finders crossed...