Note that though Henrie Pieper did not use the term "Mono-Block" he was a pioneer in their use. He was issued a patent for their construction in the US on Aug 23, 1881, it having already been patented in Belgium. Further note this was not produced by sawing off the breeches of an existing set of bbls.
I am not positive but think the term mono-block was probably coined by Berretta.

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