On page 178-179 in the book JAEGER RIFLES by George Shumway, the author says, "...They were made in the Germanic lands and in France from the mid-1600s, so they most certainly were not some new invention from the late flintlock period."
Shown on those pages is a nice over/under, believed to have been made in the mid 1700's. It had been converted to Percussion.
#508 in Pistols of the World , Claude Blair, THE VIKING PRESS, NEW YORK shows a number of Foreign rotating barreled pistols from a c1540 matchlock thru wheellocks and flintlocks some of which have up to 5 barrels.
Seems that nothing is new under the sun!