I have a small collection of stamps …joint issues…between Ireland and other countries. These include stamps from United States of America, Germany, Belgium and Mexico.
It is by no means complete. And some issues eg from Chile and Sweden would not be easy to obtain. The collection is therefore a side-interest.
Other countries eg Vatican and Britain have issued stamps which although not “joint issues” have an Irish interest. This is particularly true of Britain which often includes a stamp depicting a “Northern Ireland” landscape or personality as part of bigger “British” sets.