1976-S Proof Bi-Centennial Kennedy Half Dollar struck on wrong planchet.
We recently had the pleasure to purchase and attribute a 1976-S Proof Bi-Centennial Kennedy Half Dollar struck on wrong planchet major mint error coin.
This extremely rare Proof Kennedy Half Dollar is certified by PCGS and given a grade of Proof-67 with Deep Cameo properties.
The approximate weight of this 1976-S Proof Bicentennial Kennedy Half Dollar Struck on Wrong Planchet is 9.75 grams.
Struck on wrong planchet potential planchet match
The specifications for a US Kennedy Half Dollar planchet are 30.61mm diameter and weigh 11.34 grams.
In 1976, the US Mint struck coins for other countries. The Philippines 1 Piso planchets weighed 9.5 grams and had a diameter of 29mm and a weight of 9.88 grams, which could be a possible fit for the planchet size and weight. The 1 Piso was designed to have a reeded edge, but it is currently unknown how many reeds were around the edge of the coin ( the Kennedy Halves have 150 reeds).
Both the 1976-S and the 1 Piso planchets comprised of Copper-Nickel. Both coins were struck in the US Mint in San Francisco in 1976.
How a Struck on wrong planchet affects the coin size and reeding.
This 1976-S Proof Bicentennial Kennedy Half Dollar Struck on Wrong Planchet although slabbed, appears to display an inconsistent reeded edge around the outside of the coin. This condition occurs when a smaller diameter planchet is placed within the collar. Once the smaller planchet is struck by the minting press, there is insufficient metal to expand the planchet into the collar which applies the reeded edge. With the Kennedy Half Dollar being 30.61mm in diameter, the ideal size of the planchet BEFORE the strike is somewhere near 30.1mm.
With this Kennedy Half Dollar Struck on Wrong Planchet error, the potential planchet that was used is a Philippines 1 Piso which is only 29.0mm in diameter. This means when the coin was struck by the minting press, the collar size was probably set to 30.61mm. The 1 Piso coin diameter was unable to strike the coin hard enough to spread the coin metal into the collar all the way around the coin, the gap between the coin edge was simply too much distance.
On a Kennedy normal planchet, the usual metal travel distance for a proper strike is 0.5mm. The distance for the 1 Piso to travel over 1.61mm or three times the amount of distance to fill the collar properly.
More information on the 1976-S Proof Bicentennial Kennedy Half Dollar Struck on Wrong Planchet major mint error coin
This 1976-S Proof Bicentennial Kennedy Half Dollar Struck on Wrong Planchet shows some abnormal metal flow from the K1 to K3 (clock) position on the obverse.
This amazing wrong planchet error also lacks a solid rim from about K10 to K3 on the obverse.
The reverse of this 1976-S Proof Bicentennial Kennedy Half Dollar Struck on Wrong Planchet displays a weak rim from the K3 to K6 (clock) position.
The reverse also appears to have a weak reeded edge from K5 to K8.
It was fun to attribute this extremely rare Kennedy Half Dollar struck on a wrong / foreign planchet.
Here is a comparison. To the Left, a Kennedy struck on wrong planchet. The right shows a normal Kennedy Half.
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Not a big fan of struck on wrong planchet major error coins? Take a look at our major mint error coins called Die Caps: Die Cap Major Mint Error Coins (minterrors.org)
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