This article was published in the Australasian Coin and Banknote Magazine May 2015 and was written by the Australian Coin Collecting Blog.Subscribe here to CAB magazine.

What is a split planchet error?

A split planchet occurs when a coin splits into two halves parallel to the face of the coin. Partial split planchets (which are not covered in this article), where just part of the planchet splits away or peels off are more common and are often known as lamination peels / flaws or planchet peels / flaws.

What causes a planchet to split?

Typically it would be a poorly mixed alloy in the blank manufacturing process that contains impurities or gas bubbles. When the metal strip is rolled these impurities or bubbles prevent the metal from bonding correctly and a layer of weakness is present. This lamination flaw or weakness in the metal can, in extreme cases cover the full area of a coin planchet and cause a coin to fall apart with the application of little or no external force.

Figure 1

Split after striking – the most common full split planchet error

After the coin is struck, the planchet splits into two pieces parallel to the face of the coin. Figure 1 shows a full split planchet 1981 50 cent coin with both matching halves. The halves of this coin fit neatly together along the split faces. However, it’s much more common for the mated coin halves to be separated and for a collector to have just one side of the split coin. It’s not uncommon to find a single half of a split pre 1985 copper nickel decimal coin sitting in a collection of errors. We have seen very few split planchet bronze decimal coins, with perhaps less than 5 examples known. Having both sides of a full split planchet (a mated pair) makes the split planchet coin error worth considerably more.

In the image of the split 50 cent coin, observe the inner split face where the de-lamination occurred and note it has a typical look which is identified by rough texture and parallel metal striations. If you’re looking for a real split plancet error look for this type of texture on the split surface as it is a strong identifying characteristic.

Figure 2

Figure 3

The Clamshell – visually spectacular

Figure 2 shows, what appears at first glance, to be a run of the mill 1979 10 cent coin. However Figure 3 tells a completely different story when the same coin is viewed from the edge. This hinged split planchet or “clamshell” is a coin that looks exactly as the descriptive name suggests. A de-lamination, through a significant area of the coin, has caused it to split -but not completely. Both halves of the coin remain attached by some of the edge and the result resembles an open clamshell. The inner surfaces of the clamshell error show the tell-tale metal striations mentioned above. Take note that if the clam has been prised apart by an excited collector or unscrupulous seller, that this will devalue the error. We have seen this error on 50 cent, 20 cent, 10 cent, and 5 cent decimal coins.

Figure 4

Planchet or Blank Split before striking – rare

Figure 4 shows a spectacular and rare error in the form of a New Zealand 50 cent, this coin has been struck after the planchet has split. To form this type of error, the blank or planchet splits into two pieces some time before the coin is struck. The split piece enters the coin press and is struck. The result is a coin that is very weakly struck due to the much thinner planchet. The split side is easy to identify as it will still show tell-tale striations, particularly in the lowest points of the coin design. This is the rarest of the three types of errors we’ve discussed here, and we are aware of only three Aussie decimal coins that have been struck on planchets that split before striking.

Our last entry about the Australian 2000 $1 / 10 cent mule and the recent discovery of a new 20p mule coin error in the United Kingdom made us realise we hadn’t actually done an entry on the so called mule error. (Edit February 2016 another mule has been discovered in New Zealand -this a 10 cent/$1 mule of 2004.)

What is a Mule Coin Error?

Put simply, a mule error coin is a coin that is minted using an obverse die, a reverse die, or collar die that were never actually intended to be used on the same coin. The most well known mules in world coin collecting are the New Zealand 2c / Bahamas 5c mule (see below), the United States Sacagawea $1 / Washington Quarter mule, and the Australian 2000 $1 / 10c mule.

Undated (1967) New Zealand Bahamas Mule

What actually makes a coin a mule is subject to some debate. The above examples we gave are undoubtedly mules. The obverse and reverse dies of these coins were never ever intended to be used together. For example, the New Zealand reverse die / Bahamas obverse 2c die are from totally different countries and were never intended to be used together under any circumstances. The same applies for the Sac Dollar and Washington Quarter dies, and the Australian $1 and 10c dies. Some error specialists suggest that coins where two obverse and reverse dies are used to strike a coin are mules too and we tend to agree. Mule errors can also occur when types of dies are mis-matched, for example using a proof die with a circulation die, or even when dies from the same correct denomination are used together but not in a pairing that was intended. A good (and recent) example of this is the 2014 Britannia silver bullion coins where at least two mule errors were produced when obverse and reverse dies of the standard Britannia bullion coin were mixed up with those to be used for the Year of the Horse bullion coin.

However, a grey area rises when dies of the same denomination are used in combinations that may be normal in some years but not in others. There are examples in the Australian coin collecting area that are subject to heated debate. An example of this is the 1956y Penny ‘mule’. In this case, the normal Perth mint reverse die was used (in error perhaps) with a Melbourne mint obverse die. This is unusual, but pennies were minted in Melbourne and Perth in 1956 so some collectors argue that this coin is not in fact a mule, just a variety of the 1956Y penny.

Another example is the 2005 $1 mob of roos coin. Some collectors believe that this coin was actually minted in error (the standard $1 coin of this year was a 50th Anniversary of WW2 dollar) by the Royal Australian Mint. They believe that to cover up this error the mint simply kept producing the 2005 $1 mob of roos coin and released millions into circulation. While most sensible collectors dont call this coin a mule, there are people (usually wanting to make money on eBay) who call the 2005 $1 mob of roos coin a mule!

Whatever makes an error coin a mule, they are interesting coins to collect. And when struck from dies of different denominations from the same country, or from completely different countries they are indeed spectacular coins to look for and own.

Australian 2000 $1 / 10 cent Mule

Australia 1964 Penny Broadstrike Error

An interesting type of error is the broadstrike. Broadstrikes are coins that have been struck while the coin planchet is totally or partially unconstrained by the collar. The collar is the third major part of the coining process, and normally the blank planchet sits within the collar and when struck the metal of the planchet expands until constrained by the collar. Often this constraint is used to impart a design on the edge of the coin such as reeding.

When the planchet is free to move beyond the normal amount allowed by the coining collar the result is a ‘broadstrike’. Typically broadstrikes are thinner than a normal coin and quite a bit wider and not usually round. In addition elements of the design are usually very weakly struck or missing altogether.

Australia 2005 Broadstrike Error

Availability of pre-decimal broadstrikes depends largely on date. Early pre-decimals are very difficult to find broadstruck in any condition. George VI and Elizabeth II pre decimal coins are not too difficult to find, with the copper coins more common than the silver, and the lower denomination silver coins (3d and 6d) more common than the shilling and florin. This is likely to be the case simply because of the much larger mintages of the lower value coins. Some years are more commonly found (such as 1948y half pennies) as broadstrikes, and other years less so (such as 1951PL copper coins), Silver coins struck in the USA during World War II and 1960-64 silver can also be found reasonably easily as broadstrikes.

Those looking for broadstruck Australian decimal coins need to look no further than the 5 cent coin, with most dates from 2000 to 2005 available at most times on eBay.  Clearly those years were not good for the RAM!  One and two cent coins can be found broadstruck too, especially earlier dates (pre 1970) and 10 cent coins from the early 2000’s can sometimes be found as broadstrikes.  Larger denomination coins (20 cent, 50 cent, $1 and $2) are rare as broadstrike errors with the exception being the 2005 dollar coin (see above).   It appears that there was a problem with one die run on the 2005 mob of roos dollar and a number of broadstrike errors were the result.  They can be found from time to time on dealer’s websites and eBay.

As normal when collecting any coin you should purchase errors in the best grade that you can afford. Australian Errors are not typically graded when sold but the same sorts of standards used to grade normal circulation coins can be applied. Broadstruck coins in UNC (uncirculated) or even EF (extremely fine) condition are spectacular coins indeed!

The United States Mint has produced one of the most spectacular error coins that is available to collectors of US error coins. A dime (valued at 10 cents) was struck on a zinc coated nail either by sheer accidental contamination of the barrel of coin blanks or by Mint staff having placed it in the press for a laugh. Well a laugh we’ve had! This is one of the most impressive error coins we’ve seen and it’s for sale as well! The “coin” has been graded by PCGS as MS65 and is currently being sold by Heritage Auctions in the US. The bidding is currently sitting at $6,000USD and we expect this to rise before the hammer falls and this coin goes to a new home and is tucked away by the astute buyer.

Fred Weinberg is a leading expert in the US error coin market and has seen many rare error coins. Australian coins struck on foreign objects are truly rare (perhaps this $2 is struck on a washer) but have been seen in the RAM’s own collection of extreme error coins. Their error coin display, “One in a Million” showed the public some of the more interesting rare and valuable coin errors such as this proof platypus 20 cent struck on a bolt:

Australian 20 cent Struck on a Bolt

The One in a Million display also showed us what can happen when the press malfunctions such as this 5 cent struck on the index plate that feeds each blank in the coin collar for it to be struck. Or further below a $5 coin struck on a feeder finger.

5 Cent Struck on an Index Plate

$5 Struck on Feeder Finger

Roxbury Auction House held their auction #95 (find the catalogue here) on October 17 2015 and there were a few errors in the sale that are worth mentioning. All prices are net of commission so 20% should be added to all prices to get the final cost of the item.

Lot 644 – 10 x blanks $2 size – this lot realised just $50, surely a bargain for blanks that are worth $30 or more EACH.
Lot 645 – 1926 penny with lip – This looks like a ramstrike error which are exceptionally scarce on George V coins. It realised $300 on a $100 estimate so bidders understood how unusual it was.
Lot 647 – 1945 penny brockage – This coin is described incorrectly and is in fact a flip-over double strike, which is probably more unusual than a pre-decimal penny brockage. This was bid up to $440 on an estimate of $300 which seems to be decent value. The coin appears to have a few issues with carbon which probably held it back from a bigger number.
Lot 648 – 1988 $2 with major bitten flan – this one snuck under the radar and fetched just $80 on a $90 estimate. Seems a bargain considering the clipped planchet in the image below sold recently for just over $500 in a private sale. The coin below is a better grade and a larger clip and thus has a higher value than the coin in the auction. But never fear dear reader if you want the 1988 clipped dollar that was sold in the auction an enterprising individual has it up for sale right now on eBay for $500.

$2 Large Clipped Planchet Error – Unknown Year