It's very common among Germans and I understand that it's not unknown among the Polish
I was refering to the Three Kings picture. Were you as well? I'm half German and have never heard of this.
Whoops, I only half-read your post. I do know that, as late as the 1970s, Holy Trinity German Catholic parish in Boston distributed holy cards of the Magi and, if I remember correctly, the prayer was on the reverse. Keep in mind that the Sainted Bishops are much venerated in Germany, where they are (I believe) the patrons of the Archdiocese of Cologne and are represented in the coat-of-arms of the city itself.
The Cathedral of Cologne is the depository of their relics (yes, taken from the East) and it is among the largest - if not the largest - reliquary in Christiandom.
