Ted;
I am not saying that Regis Darne did not obtain a patent on a monoblock of some kind. My "IF" is to whether it was the concept of the monoblock or just some mod of it.
As a good example I have read probably a thousand times that Samuel Colt "Patented the Revolver". If you read his patent you will find that he did in fact "NOT" patent the concept of a revolving cylinder. He in fact patented the hand & bolt, connected to the hammer for the purpose of rotating the cylinder & locking it in alignment with the bbl upon cocking the hammer. The concept of the revolving cylinder itself had been tried & used to some extent for at least Two Centuries prior to "Ol Sam Colt".
I was simply giving some possibilities of how He "Might" have received a patent on the monoblock principal, Still not sure that he did. Until such time as I can read that patent or here it from someone who understands it I have not the slightest. To be totally honest you are just too prejudiced to be a truly accredible account.
My real thinking is that Pieper did file his patent in France & that Darne simply filed for some slight modification. After Pieper's patent had expired then any maker could have used his features, just not the portion which Darne held the patent on.
There are of course still many makers even today who are still not using this design, many prefer other methods. In fact there are many who still consider the chopper lump superior to the monoblock.
I very seriously doubt that the use of the monoblock made a vast difference in how many guns Darne sold. I really think that the reason most either bought or did not buy a Darne was based primarily upon their view of the sliding breech, not the method of joining the bbls.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra