The Australian Numismatic Society

A Paper given at the June 2020 online Conference

A Study of Off-Centre Strikes and Coinage Press Die Placement:
Australian Pennies and Halfpennies  by  Paul M. Holland

 Off-centre strikes occur when the coinage blank or planchet is struck while not properly seated within the collar of the coining press.  If a significant portion of the
 planchet lies outside the collar the coin will only be partially struck, creating an off-centre error coin. Of special importance to the present investigation is that off-centre
 error coins tend to be bent or ‘cupped’ when the planchet is squeezed against an inner edge of the collar by the downward force of the moving upper die. This ‘cupping’
 feature clearly reveals the orientation of dies in the coining press. For example, if an off-centre coin is cupped toward the obverse, then the obverse die was positioned as
 the upper or “hammer” die the coining press at the top and the reverse die as the lower or “anvil” die. It should be noted, however, that not all off-centre coins show this
 cupping effect clearly enough to reveal the orientation of the dies in the coining press.

 This can provide valuable numismatic information on predecimal coinage, since the orientation of coinage dies is not otherwise recorded in mint records. Thus the only
 way to ascertain die placement in coinage press it is by the study of off-centre strikes. Unfortunately, such error coins are relatively rare (and often expensive) making
 comprehesive study of them difficult. I’ve been slowly accumulating examples of these for more than twenty-five years and with a number of acquisitions made during my
 visit to Australia in 2017, this now allows me to extend my previous work on pennies[1] to halfpennies, and to provide more comprehesive results for Perth mint pennies.

  Examples of pennies struck off-centre at the Perth and Melbourne mints, respectively, are shown in Figure 1. These reveal that the obverse die was positioned in the
 coining press as the upper die for the 1945 Perth Mint penny, while the reverse die was on top for the 1949 Melbourne Mint coin.

Figure 1.  Examples off-centre pennies struck at the Perth and Melbourne mints.

Fortunately, it’s possible to independently confirm this orientation for Perth mint penny dies based on a radio script from 1945 in Perth mint records. In the transcript,
Mr HL Moore, the Foreman of Machinery, explains that

The bottom die for the reverse side is a fixture and the obverse or head die is fixed in the moving head. As the blank is fed on to the bottom die the moving head comes
 down and stamps the piece, which as you see is held by a surrounding steel collar. So both impressions are given to the coin at the same time.[2]

The unusual observation of a reversal in die orientation for bronze pennies between the two mints is clearly highlighted in the survey of forty off-centre strike pennies in my
 reference collection shown in Table 1. Note that in one case I’ve supplemented these results using an auction photograph for a 1964 Perth mint penny where the die
 orientation was clearly discernable. The most important new finding in these results is clear evidence that both coining press die orientations are now clearly observed for
 Perth Mint pennies of 1962-1964. More on that later.

Table 1. ‘Cupping’ orientation of off-centre error pennies by date and mint.

    Date         Mint    Orientation  Number of coins

    1941 K.G  Perth    Obv            1
    1942 Y.    Perth    Obv             2
    1943 Y.    Perth    Obv             1
    1944 Y.    Perth    Obv             4
    1945 Y.    Perth    Obv             1
    1947 Y.    Perth    Obv             1
    1950 Y.    Perth    Obv             1
    1952 A.    Perth    Obv             1
    1953 A.    Perth    Obv             1
    1957 Y.    Perth    Obv             1
    1959 Y.    Perth    Obv             1
    1960 Y.    Perth    Obv             1
    1961 Y.    Perth    Obv             3
    1962 Y.    Perth    Obv             1
    1962 Y.    Perth    Rev              1
    1963 Y.    Perth    Obv             1
    1963 Y.    Perth    Rev              1
    1964 Y.    Perth    Obv             1
    1964 Y.    Perth    Rev              1*

    1947    Melbourne    Rev            1
    1948    Melbourne    Rev            2
    1949    Melbourne    Rev            3
    1950    Melbourne    Rev            3
    1951    Melbourne    Rev            1
    1952    Melbourne    Rev            1
    1964    Melbourne    Rev            5

Obv = Obverse is upper die; Rev = Reverse is upper die; * from auction image.

Examples of halfpennies struck off-centre at the Perth and Melbourne mints, respectively, are shown in Figure 2. These reveal that the obverse die was positioned in the
 coining press as the upper die for both the 1963 Perth Mint halfpenny and 1959 Melbourne Mint coin.

Figure 2.  Example off-centre halfpennies struck at the Perth and Melbourne mints.

A survey of coining press halfpenny die orientation revealed by seventeen off-centre strikes in my reference collection is presented in Table 2. This includes results for
 some sixteen Perth mint halfpennies from 1945 to 1963, but only a single 1959 entry for Melbourne. This is perhaps understandable since after 1944 virtually all halfpenny
 production had been transitioned to the Perth mint, with the only two halfpenny dates struck at Melbourne being 1948 and 1959. The Perth mint halfpennies examined all
 show the obverse to be the upper die, including twelve from the years 1945-53, together with four from 1961-63.

Table 2. ‘Cupping’ orientation of off-centre error halfpennies by date and mint (see text).

    Date    Mint        Orientation    Number of coins

    1945 Y.    Perth    Obv            1
    1946 Y.    Perth    Obv            1
    1947 Y.    Perth    Obv            1
    1948 Y.    Perth    Obv            4
    1949 Y.    Perth    Obv            2
    1951         Perth    Obv            2
    1953 A.    Perth    Obv            1
    1961 Y.    Perth    Obv            3
    1963 Y.    Perth    Obv            1

    1959    Melbourne    Obv         1

Obv = Obverse is upper die

So why should this information be of numismatic interest? Besides providing unique information about the orientation of dies in coining presses, this seems to offer the only
 way to explain why ‘strike-doubled dates’ are relatively common among Melbourne mint pennies, but are not observed on those from the Perth mint. Such coins have
 incorrectly been described over the years as being ‘double struck’ or having ‘re-cut’, ‘re-entered’ or ‘re-engraved’ dates’. For example, John Dean lists such Melbourne
 mint pennies for 1948, 1950 and 1951 with catalogue numbers P48A(a), P50A(a), and P51B(a).[3]  Foster shows these for Melbourne mint pennies of 1948, 1949,
 1950, 1951 and 1952 in the first edition of his book (P50, P51, P53, P56, P57).[4]  Interestingly, neither author lists any for Melbourne mint halfpennies or Perth mint
 bronze coins. I show examples of such ‘strike doubled dates’ on Melbourne mint pennies from my reference collection in Figure 3.

Figure 3. Melbourne Mint pennies with strike-doubled dates.

In fact these are error coins, with no two precisely alike. They are the result of a process known variously as ‘strike-doubling’, ‘mechanical doubling damage’ or
 ‘machine-doubling’ that  is believed to be caused by looseness in the die or coining press mechanism. This allows movement of the die while it is still in close contact with
 the newly struck coin. Here, a momentary lateral motion can be imparted to the loose die allowing it to rebound during this vibration and drag across the face of the coin
 as it withdraws after striking the coin. This can produce the flat areas of damage that are characteristic of strike or mechanical doubling. I’ve made precision
 measurements of the displacement shown in these flat areas on Melbourne Mint pennies and my results reveal the largest to be 0.3 mm, or about 1% of the diameter of
 the coin.

Because areas on the coin with the sharpest changes in relief are most affected, strike-doubling is especially noticeable at the date (a part of the coin which is almost
 always carefully examined by collectors). However other parts of the design are also affected, for example note clear evidence of “strike-doubling” at the bottom of the
 kangaroo’s tail just above the dates in Figure 3.

Typically only portions of a coin are affected; for example, several letters of the legend may exhibit strike-doubling but the date will not, or sometimes only a few of the
 date numerals may exhibit doubling. The close resemblance of coins with strike-doubling to coins made from doubled dies can be a source of confusion for collectors.
 Generally, strike or machine doubling exhibits flat ledge or shelf-like areas, whereas the features on doubled dies are typically more rounded and will often show both the
 doubling of portions of letters and the ‘splitting’ of serifs (which are due to hub misalignments when pressing the design into the die during manufacture).

The results of Table 1 also show that both orientations of obverse and reverse penny dies in the coining presses at the Perth mint first appeared sometime during 1962, and
 both positions are observed each year from 1962-64. This seems to coincide with two new coining presses coming into service at Perth in 1962 in addition to the five
 already in use.[1] Here, Press #7 began striking pennies on May 30th, followed by Press #6 on July 3rd. Although the reason for both die orientations is not understood,
 it may be that these new coining presses were set up differently.

Previous survey results for some 305 Melbourne mint pennies with strike-doubled date from 1947-1953 in my reference collection are shown in Figure 4 as the dark
 bars.[1]  It should be pointed out that this is simply a raw count of the number of these coins observed in my collection, and is not a statistical sampling. Even so, the
 results show a pronounced upward trend for the years 1948 to 1952, with a very sharp reduction in 1953, dropping from 89 coins in 1952, to only four in 1953. If a
 relative comparison of these results to mintage figures (in millions, light colored bars) is plotted using the same scale, the years 1949-1952 show a substantial relative
 excess (i.e the problem became worse). The sharp drop in 1953 suggests that strike or mechanical die doubling was probably recognized as a problem at the Melbourne
 mint by late 1952 and that corrective steps were taken. However, without access to detailed Melbourne mint records for this period, precisely what occurred is unclear,
 although it seems likely that either repairs or maintenance to the offending coining press (or presses) were made and improvements in the regular maintenance schedule
 were probably instituted.

            Figure 4. Distribution of 305 Melbourne mint pennies with strike-doubled dates compared to mintage figures (see text).

It should also be pointed out that in 1953 a substantial reduction in the relief of the reverse die from 1/2 to 3/8 relief or by 25% was being instituted, and this was the
 source of some controversy at the mint.[5] Although in fact, 1953 long 5, different 3 Melbourne pennies with the new lower relief reverse are rare coins, amounting to
 only a few percent of the 1953 pennies struck in Melbourne and none of these appear in my Figure 4 survey.

In conclusion, the study of off-centre strike coinage errors offers an unusual approach for extracting numismatic information and may lead to important new insights.  In the
 present case, an examination of off-centre penny strikes reveals differences in the placement of obverse and reverse penny dies in coining presses at the Perth and
 Melbourne mints. This helps explain why pennies with strike-doubled dates are so common in Melbourne mint pennies compared to those from the Perth mint. In
 extending this study to off-centre strikes of predecimal halfpennies, no differences in die orientation between the Perth and Melbourne mints are seen, with the obverse
 always being the upper die. This is consistent with no strike-doubled dates being observed in these coins.


The author would like to acknowledge Bob Roberts and Joe Dettling of M.R. Roberts for their help in obtaining off-centre strike pennies and halfpennies crucial for this study. 


1. Holland, Paul M., “Numismatic Information from the Study of Coinage Errors”, Journal of the Numismatic Association of Australia, 14, 2003, pages 41-46.

2.   Personal Communication from Anthea Harris, Records Coordinator and Curator, The Perth Mint, of an ABC radio transcript recorded 22 August 1945 and
 broadcast on 12 October 1945 at 9:08pm through 6WF and regional stations, Perth Mint record PM5717; together with other information from the Perth Mint
‘Die Account’ book.

3. Dean, John.  Australian Coin Varieties Catalogue, 1st edn, Hawthorn, Melbourne, 1964.

4. Foster, Derek J.  Catalogue of Australian Coin Varieties, 1st edn, Blacktown Auctions, Blacktown, NSW, 1964.

5. Holland, Paul M., “Mystery of the ‘Missing’ Reverse Die Type for the 1953 Perth Mint Penny”, Australasian Coin & Banknote Magazine, Yearbook
December 2017/January 2018, pages 8-10.
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13th June 2020