Usually a collector avoids double or triple items. But sometimes they lead to discoveries. Did you know for example that in the 19th-century print shop it was common practice to apply what we could call lithoshopping on the limestone plate? Look for yourself.
In fact, some publishers shamelessly recreated on the stone almost identical copies of the covers originally published in another country.
And then again, one Pas de Quatre is not the other Pas de Quatre, or is it?