The Clamshell Coin Error

Australian 1950 Threepence Clam or Hinged Planchet Error

Australian 1950 Threepence Clam or Hinged Planchet Error

You often see flaws in the metal blanks used to strike coins but rarely do you see coins so obviously wrong as the clamshell error. These planchets contain lamination problems deep inside the metal which splits the 2 sides apart with only a hinge holding the coin together. While not always possible to store these in a 2×2 holder I have seen these stored in flip top coin boxes as they are very much 3 dimensional objects.

The Australian threepence seen above has probably seen some human involvement to prise the 2 sides apart, but never the less an interesting example of this type of planchet defect error. The lamination flaw, weakness or impurity ran through the centre of the coin allowing it to split open. The flaw may have been caused by the alloy not being mixed properly when the blanks were being prepared or a foreign material or gas being trapped inside the blank as the sheet metal was being rolled.

If the weakness ran through the entire body of the coin and each side of the coin became separated it would end up looking like a complete split planchet coin.

Click image to enlarge

Posted in Error Coins

Site Search


Upcoming Coin Collecting Events:

no event

Australian Numismatic Calendar

Current Coin Values, Bullion Prices and Exchange Rates

AUD $15.09
Australian 1966 Round 50c
AUD $818.86
Gold Sovereign
AUD $1,025.10
Australian $200 Gold Coin
AUD $44.19
Silver Price (per Oz)
AUD $3,478.28
Gold Price (per Oz)
USD $0.6594
Australian Dollar

These values are updated hourly using New York market prices. Coin values are purely the value of the gold or silver they contain and do not account for any numismatic value.
Prices Last Updated: 08:04 10 Jun 2024

Subscribe via Email

Enter your email address to subscribe to the Australian Coin Collecting Blog and receive emails about new posts.