Error Coins - Planchet Errors - Part 3


This article gives out information on types of error coins. As the number of error coins classification is quite large, the article is divided into 6 Parts.

Part 1: Design Errors
Part 2: Die Making Errors
Part 3: Planchet Errors
Part 4: Strike Errors
Part 5: strike Errors Continued
Part 6: Mules



Planchet Errors:
This section gives out the details of the errors that can occur during creation of Planchet.

Incomplete / Chipped Planchet:
In this type of error, the Blank Planchet used to mint the coin is not of correct shape. This happens when the Blank is being created out of the metal sheet. There are multiple ways in which this error can happen. These are classified as; 

  • Rim Clip: Very small curved or straight portion of the rim/edge missing. 
  • Incomplete Clip: Long incuse curves on Obv. & Rev. due to an incomplete blank punch overlapping a previous punch. Considered Rare. 
  • Straight Clip: Similar to a Rim Clip only with a larger portion of the edge (2-3%+) missing along a straight or slightly bowed out line. 
  • Corner Clip: Coin struck on planchet created by a blank punched from the corner of metal strip. Very rare as only four even possible per roll of metal. 
  • Curved Clip: Similar to a Rim Clip only with a larger portion of the edge (2-3%+) missing along a inward curved line. 
  • Ragged Clip: Jagged fairly straight portion of the planchet edge missing. Considered a Defective Planchet if not straight and runs deep into planchet. 
  • Elliptical Clip: Oval shaped coin due to a complete blank punch overlapping a previous punch. Normally 'Elliptical' & 'Crescent' Clips created together. 
  • Disk Clip: Similar to a Rim Clip only even smaller and along the rim's edge. Seen on the Edge as an tiny indent or dip along the coin's copper core. 
  • Assay Clip: Blank/Planchet with a portion missing as if cut out. Very Rare. 
  • Crescent Clip: Similar to a curved clip only with 50% of the coin by wt. missing in an inward curve. Normally the other smaller half of an 'Elliptical Clip'. 

Below are some of the error types I found in the Indian coinage.

Type 1: Curved edge. This happens when the sheet does not move ahead by sufficient distance. The next punch will overlap an already punched area. This causes edge to have a curve. See images below.

Type 2: Double Curved edge: This happens when the sheet does not move ahead by sufficient distance and at the same time also moves sidewards [Sideward movements are not desired]. This causes a double curve.

Type 3: Straight Edge. This happens when the metal sheet is not feed correctly into the Blanking Press. The other way this can happen is during the advance of the metal, it also erroneously moves sidewards. The coins are punched towards the edge. This results in one side of the Planchet being straight.

Type 4: 2 Double Straight Edges. This is similar to Type 2, except that the blank is being stuck in the corner.

Type 5: Ragged Edge. This is similar to Type 2 or Type 3, except that the metal sheet being used here does not have a straight edge, but a highly uneven jagged edge.









Note:
It is important to note that at times these errors in coins can be intentional outside the mint. i.e. Fake Error Coin. The way to identify if a coin was chipped during the Blanking process or after it has been stuck is to observe the relief in design, especially near the cut portion. A coin which was stuck with a chipped planchet will show weakness in strike near the cut area; this is because the metal instead of flowing into the die expands outwards. The edges themselves will be more rounded that straight if cut later. The 10 Paise aluminium coins above look like cut after the coins left the mint.



Uneven Planchet Surface:
Normally the sheet used to create blanks / planchets has even and smooth surface. However at times due to impurities on the surface the sheet at places may not be smooth. At times its also possible that during transportation or handling, there are abrasions on the surface on the sheet. A planchet created from this area will still have the imperfection, the resulting coin will still show the imperfection and the metal flow is not sufficient to cover this up.

A good way to identify if the abrasion is not cause after minting and during circulation is to see the image on the coin, if it was there before strike; it will still show a weak imprint on those area’s. If it was after minting the coin, then there will be no imprint in that area.

Below an Rs 1 coin stuck on an imperfect planchet.




Missing Center
This is a new type of error in the Rs 10 Bi-Metallic Design. In this type of coins, there are 2 metals used of different combination. These are then fused under pressure. Sometimes the coins do not fuse well. The center piece comes off from the outer ring during the minting process. Thus the coin would be without a center piece. There would be other type of error where only the center piece is available and the outer ring is missing. However if the center piece is stuck offcenter, then it’s a Planchet error. If the strike is centered, it indicates that both the pieces of the Planchet was correct during the strike and came off after the strike.



OMS [Off Metal Strike]

This type of error happens when the coin is minted on a metal that it is not intended for. There are 2 ways in which this can occur;

One is the metal alloy that is being used to strike the coins comes in different alloy mix percentage than specified. For example the Ferritic stainless steel [FSS] used for the current coins is a combination of Iron 82% and Chromium 18%. If the metal delivered to mint comes in say more Iron content, say 90%, then the coin will be more Iron and will have different characteristics than the FSS.

The second way this can occur is if there are 2 coins being minted with similar metal [not distinguishable easily to normal eye] and there is a mix up in the feeding the metal alloy sheet to the blanking machine. For example from 1964 to 1971 the 50 Paise was minted using Pure Nickel, the 10 paise from 1964 to 1967 was minted in Cupro Nickel and from 1968 to 1971 it was Nickel Brass. All the metals look same in raw form and develop distinctive toning after finishing. Hence if Cupro Nickel sheet was used to mint the 50 Paise it would have been OMS. Note that for the coins specified there was a slight difference in thickness of the coins [which means that the OMS coins would have been of different thickness as well].

There are very few known and accepted OMS error coins in Republic India coinage.


1984 25 Paise coin
Below is an image of 1984 25 Paise coin that has more Iron content and hence magnetic. The actual metal for the year should be cupronickel. As to how this is possible is not known as Indian Coinage adopted Stainless steel for coins only in the year 1988.


2003 Rs 2 coin
Another coin is the 2003 Rs 2 coin that was minted using steel rather than cupronickel. This is possible as during that period Rs 1 coins were minted using steel, the diameter as well as thickness of the Rs 1 coin is similar to the Rs 2 cupronickel.




2003, Calcutta Mint
Another OMS struck in Cupro-Nickel in stead of stainless steel in the year 2003, one rupee coin.


Note: The size and thickness of the Rs 2 Cupronickel and the Rs 1 Stainless steel coins was similar. The above error could also be “Stuck on wrong Planchet” type of error [see section below]. As explained in more detail in that section, this can also occur due to stray planchets finding their way to incorrect pair of dies. So rather than classifying these as OMS, I am more inclined to classify these as “Struck on wrong Planchet”.


Thin / Thick / Weight Error:
This type of error occurs when the metal used for creating blanks is of different thickness than specified or is not rolled correctly for even thickness.

This error is typically on the metal sheet that the mint has procured and has failed prper quality checks. The thickness error can be both ways; i.e. the metal is of more thickness or of less thickness. This type of error is relatively rare.

The more common thickness error is as a result of the sheet not being rolled correctly of uniform thickness. IE the sheets tapers off upwards or downwards from one end to another end or is uneven in thickness throughout. It is more possible that this type of sheet can pass the quality checks.

There are supposed to be quite a few coins of Rs 2 cupro-nickel minted in 1997 from Hyderabad mint that are almost double the desired thickness or almost half the thickness, ie instead of 6 g, the coins are aprox of 9 g and 3 g. However I have not seen or come across such coins.


Split Planchet, Before Strike:
The Planchet splits into half before being struck because of improper metal composition used. Thus the coin will be exactly half as thick as desired. The strike itself would be weak as the pressure exerted by die is less.


Sintered Planchets:
In the process of creating Planchets, Blanks are often cleaned [to remove any dirt] and bathed in a chemical [to give distinctive toning]. During this process at times, the operators forget to replace the chemicals used for a previous batch run. Thus we have a dirty solution used to previously clean coins of different metal composition. This leads to trace amounts of other metal getting stuck to the surface of the Planchets being cleaned.This causes discoloration in pockets or in the whole planchet. Coins stuck with this Planchets will show discoloration.




4 comments:

  1. I have got one 2 rs coin on the theme 150 years of railway which is mintef in fss instead of cupro nickel. What should be the approx price of this coin and also thr rarity

    ReplyDelete
  2. This would be quite rare. Generally happens when the blanks from previous run got mixed up with the next run. There is no fixed price for such coins. It depends on how desperate and rich the buyer is.

    ReplyDelete
  3. sir can u explain me why every country`s coin one common design pattern.why value of coin is not minted on both side?why only one side?please provide any reference.

    ReplyDelete
    Replies
    1. This is not true. There are few countries where value is on both sides. Even the Indian coin of unity in diversity/cross have value on both sides

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