Gunnery in the 17th Century was part science and part craft, but there was no substitute for experience in the field. The Master Gunner would be a civilian, richly dressed, well paid and not above swapping sides or returning to Europe's wars if the pay was not to his liking. Marksmen were rare in the Civil wars, but turn up in certain Swedish regiments in the Thirty Years' War in a regular fashion. Marksmen were principally used in sieges, where they were employed in towers to pick off besieging gunners and specialists, or in the siege lines where they tried to do precisely the same thing back.
This contains 1 Master Gunner Hertz Van Rental 1 Old Tom, Marksman