1951 halfpennies were minted in Perth, London and Birmingham. Note that no 1951 dated halfpennies were minted in Melbourne. The London and Birmingham coins carry the 'PL' mintmark, the Perth coins have a dot after the Y (common) or no mintmark (scarcer). The no mintmark halfpennies seem to comprise roughly 10% of the total Perth mintage.
During 1951-1952 the Perth mint began producing their own dies. The early 1951 dated dies were obtained from Melbourne, the later dies made locally from master dies obtained from the Royal Mint. The reverse dies sourced from Melbourne had the dot mintmark after the Y of HALFPENNY, the locally produced dies had no mintmark.
There is also a difference in the date. As can be seen in the following pictures, the final 1 in the date for the 1951 Y dot halfpennies appears at first glance to be much longer than for the 1951 plain and 1951PL, which are identical as the master dies were derived from the same source. Closer inspection however reveals that it is actually the 5 on the 1951Y which is shorter than the 5 on the 1951PL and 1951 plain.
The new obverse (obverse 5 or "1952 obverse") sent out from the Royal Mint was also different to the one that was being used (obverse 4 or "1949 obverse"). The two obverses have a different number of rim beads and the difference is easiest to see by looking at the I's in FIDEI - those of obverse 4 align with beads, those of obverse 5 are between beads.
|1949 Obverse (Obverse 4)||1952 Obverse (Obverse 5)|
The result of all this is that there were two distinct reverses and two distinct obverses used to produce the 1951 Perth halfpennies. Now if production of halfpennies using the old dies had ceased when the new dies came into commission and the new dies were used exclusively afterwards, then we'd have just two different combinations of die pairings (1951 Y with obverse 4 and 1951 plain with obverse 5). But there was a changeover period during which both the new and old dies were used to strike coins.
We find some 1951 Y halfpennies with obverse 5 (roughly 10% of the 1951 Y) and very occasionally a 1951 plain with obverse 4 (about 1 in 25 of the 1951 plains). From examination of the die records of the Perth Mint, Paul Holland in the Journal Of The Numismatic Association (Vol 10, page 32) deduces that there was one die-pairing of the 1951 plain with obverse 4 that yielded a total of 126,720 coins struck. This is consistent with my obversations from going through close to 10,000 1951 halfpennies at Downies - about 1 in 25 of the 1951 plains have obverse 4 and the 1951 plains comprise about 1 in 10 of the 1951 Perth mintage. This makes the 1951 plain with the 1949 obverse (obverse 4) the second scarcest halfpenny after the 1923.
|Reverse Die||Obverse Die||Mintage|
|1951 Y||Obverse 4||about 23 to 25 million|
|1951 Y||Obverse 5||about 2 to 3 million|
|1951 plain||Obverse 4||126,720|
|1951 plain||Obverse 5||about 2 to 3 million|
Note also how the 1951 plain has a mintage closer to the reasonably scarce 1952A halfpenny than to the 1951Y, indicating that it is undervalued in the catalogues.
It is an important fact that these halfpennies are well known to suffer die fill. In particular I have seen this occur on the mintmark of the 1951Y to the extent where the mintmark has been completely obliterated, thus making it at first glance appear the coin is a rare 1951 plain with obverse 4. The 1951 plain and 1951Y differ in the date as well, so it is important to check the date also before celebrating a 1951 plain, obverse 4 find.