OMG,what a bunch of Anglophile shotgun lovers who who never heard about "The Other Mr.Churchill" (title of a book) and his XXV shotguns with "Churchill ribs"!
The E.J.Churchill firm was founded in 1891. After E.J.'s death in 1910 the firm was run by his nephew Robert Churchill, 1886 – 1958. The firm was then amalgamated into Churchill, Atkin, Grant & Lang. C, A,G & L ceased to trade in 1980.
Robert Churchill worked as a forensic ballistician too, and operated his own shooting school, but he is best known for his book "How to Shoot", 1955, later expanded by Hastings. some finds on the net:
http://www.doncurrie.com/churchill-method-of-shooting
http://www.amazon.com/Robert-Churchills-Game-Shooting-Wingshooting/dp/0924357118
http://www.abebooks.com/book-search/title/game-shooting/author/robert-churchill/
Myself, I learned the halfway proper use of a shotgun with the help of the German translation of his book, "Das Flintenschiessen". As a result I bought a second hand Spanish Aya XXV boxlock many years ago.
Post-WW1 propagated the use of short, 25", shotgun barrels for game shooting. As some people complained about the barrels appearing " stubby" when aiming over the rib, Robert Churchill invented the narrow rib to create the illusion of a much longer barrel. His speciality was the Churchill XXV shotgun, aptly named so for the barrel length. So such a narrow rib is commonly known as a "Churchill rib". On order his guns were available with conventional longer barrels too, but he discouraged their use. Besides some over-unders available on order, Churchill recommended side by sides. In his book he favored boxlocks, as they balanced better in his opinion. He offered two grades of sidelock s/s, named "The Premiere" and "Imperial", and three boxlock grades, the "Hercules", the "Regal" and the "Crown". So the "mystery" of the crown engraved on your gun is solved.
Later, his style of guns, boxlocks with 25" barrels and Churchill rib, were copied by other gunmakers like Greener and Aya, as a demand was kept alive by his book and fame.