This is an unusual question for a philatelist, but almost obvious for a numismatist with an answer that sounds yes. We are stamp collectors, with for most of us limited or even no interest for coins. Therefore, coin collectors will definitely be able to provide a better description of joint coin issues. Over the past 20 years, while looking for joint stamps, it happened that we encountered some surprising joint coin issues. We came to the idea that a page for this type of products should be opened in our catalogue, just to trigger the attention about the similarities with joint stamp issues. A first, absolutely not exhaustive list, with limited description, but including all illustrations, was made available as a new chapter at the end of Vol 1 of the catalogue. If some collectors answer to this mail by providing additional joint coin examples, we may consider extending the section. Actually, so far, less than a dozen of common issues have been found, but the search was not made in an extensive way and most of them were found per pure chance. Also, as it is not our core interest, this chapter may stay at this level for a long period. However, for the purpose of coherence, we already introduced the new category [K] (a letter staying obviously for ‘coins’). If this article triggered your attention, have also fun with this treasure search!
On the basis of this first short list, it became interesting to discover that with coins, we can encounter the same type of sub-categories as with stamps. Twin coins (same design, same date of issue) [TK] do exist, such as in 2005 with Australia and New Zealand (ANZAC) or in 1999 with the Marshall Islands and Zambia (Elephant). As exact issue dates are difficult to find (no first day cancellations 😉 ), Concerted coin issues [CK] have not been identified, but parallel coin issues (same date of issue, actually both countries’ coins sold together in a folder, but different designs) [PK] have been see for example recently (2021), involving Canada and UK. More surprisingly, we could create the sub-group of Unique issue; i.e., a coin used by two different countries with names of both countries on the same coin [UK] such as the Dubai – Qatar currency used between the years 1966 and 1973, while Se-tenant coins (coins split in two halves, each one for one country) [SK], have been seen with Kiribati and Samoa in 1997 or Poland and Ukraine in 2012.
You will find below some examples of joint coins, and we would like to welcome any information from numismatists who could help update our information level.