Greetings from Western Australia all.
I have an interesting 1935 Farthing with a concave on the reverse and convex on the obverse. It has been in a box with other coins for at least 42 years (when Grandad passed and Dad bought back to Australia)and probably many years longer. First instinct is to think PMD. Then the process of working out how? Someone said that probably used as a wedge under a table or something heavy to balance it and this has happened over many years. Sounds reasonable but then if used to balance then not much weight on it. They hit the coin dead centre and no damage to the coin at all apart from the doming. Physics says to me that the harder object wins so even with a heavy weight what ever was touching the coin would either submit to the pressure or the Britannia would submit to damage before the coin would dome? The Royal Mint Museum has confirmed the below. So whilst no certain proof, it allows for the possibility of a minting error. However my thoughts are that even though there were only 2.2m or so 1935 Farthings minted surely if a mint error, there would be more than one and I am yet to find any reports anywhere of such. So anyone that has any 1935 Farthings could they please check for domes and let me know? I have had the coin checked by a dealer who confirmed no apparent damage to the Britannia reverse. Would love to hear from anyone that has seen or possesses any such coin/s and any ideas on how the dome could have been formed post minting?
"I have now had chance to share the images you have kindly provided with our Information and Research Manager, and we have compared it with those coins the Museum has in the collection and has encountered previously.
It is possible that the appearance you describe might be a result of the size and scale of the George V portrait of coins of this era. The nature of a large and high relief portrait is that it can, when struck, draw too great a portion of material from the reverse of the coin. This issue was a particular concern for the George V portrait on the penny, and in 1933 experiments were undertaken to try and produce a lower-relief, smaller portrait, to eliminate a ‘ghosting’ effect which had been observed on the reverse of some strikes. It may be the case that this same problem has resulted in a very slight concave/convex effect on your farthing, although it is unfortunately very difficult for us to say with any certainty, and particularly from photographs alone"