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https://en.numista.com/catalogue/pieces1342.html)
Hello!
I feel like more information/testing is needed for a comment like this to be added to the coin's page. While 1971 may be 0.5 millimetres larger, a comment like "1971 is 0.5 millimetres larger than all other years" may not be accurate since coins of 1972-1974 have not been tested.
Also, exact measurements would be preferred. The page currently says these coins are 25 millimetres, but a smaller coin or a larger coin could have been measured for that (or maybe that is the average).
So, if you are able to gather more information, I will make a request to add it to the coin's page. But with the information that was provided, I do not think it is enough. But of course, if you really want that information added, I will not stop you from requesting it yourself.