Lovely scans Andrew,
the post is not too long.
I am a huge fan of Mouchon, but know very little about him
just the stamps he has engraved.
Being French his story probably exists locally somewhere.
I know him mainly from 2 things, his famous issue
"The rights of man", and his worldwide controversy, when he
engraved a stamp of Serbia with a image of King Alexander 1st.
Some sensationalist blockhead stamp collector, one would assume,
decided he saw a "death mask" hidden in the engraving,
if you turned the stamp upside down, balanced on one foot,
and saw the image in a mirror.
What an outrage for a well meaning and brilliant artist.
He was so upset at the accusation, he never engraved
philatelically after that, and we were deprived of further
examples of his genius.
Some of his catalogue of work.