So I was looking at yearly average historical Silver prices, and from 1959 onward the value of the silver was greater than the face value of War Nickels.
1.00 of war nickels contains 35 grams of silver, or 1.124 Troy oz, so at prices of 0.90/ozt or higher the silver value exceeds 5 cents a coin. In 1964, with silver at 1.29/ozt, a dollar of 90% silver coins only contained 93 cents in silver, whereas the dollar of war nickels had 1.45 worth of silver.
You'd think the war nickels would have been hoarded earlier and even more energetically than the 90% silver, but as already observed they are still found occasionally in circulation. I'm glad the mint created these unusual coins.