Here is my mystery for the day.

In contrast to the superbly detailed images above, Jean E. Lorenzi was a man who created simple images using the minimum
of lines. That is not to say that he was not a fine artist but as much
of his work was caricature it would be possible to dismiss him as simply a cartoonist. A simple internet search shows many drawings where he has captured the full range
of human expression with his few lines. Which brings me to his
stamps...

Death Centenary
of Frederic Ozanam

De La Salle commemoration.
Lorenzi designed several
stamps for Monaco, several
of them with this reverse engraving. If I saw this on a modern stamp I would think it was computer engraved but this was in 1954 and the punch card machines
of that time were not capable
of imagery.
In my opinion, it would have been an exceptionally difficult piece
of engraving to produce this simple image. And that brings up the question
of "Who was the engraver?"
A French stamp site that I visited had no doubt that Lorenzi, himself, was also the engraver and his is the only name on the stamp. At that time, with all the other Monaco
stamps, that meant he did both.
However, on all the sites I have found
of his work, none mention him as being an engraver as well as an artist or calligrapher. Surely if he was good enough to engrave these
stamps, he did other engravings as well. If anyone can show some
of his other engravings, or knows more about this artist, I'd appreciate it if you could post it here.