Most of you guys follow TheCoinShow on Facebook and Twitter and have already seen this, but those who are out of the loop need to check this out. https://www.coinworld.com/voices/bill-gibbs/2015/09/transitional_errors.html?utm_content=buffer13905 1971 D silver-copper clad Kennedy half discovery! Only took 44 years this time compared to the 1919 DDO Merc.
It could also conceivably be a Panama half balboa planchet. These were minted on the same silver-clad planchets that the half dollars of previous years were. Although the 1/2 balboas were minted in San Francisco, it's likely the planchets were shipped over from Denver.
@silentnviolent you beat me...I saw in my FB feed from ANACS Here's Coin World's video on the error... http://www.coinworld.com/videos/2015/september/monday-morning-brief-september-21-2015.html