4.7"/45 (12 cm) QF Mark IX & XII (3rd down of the 4.7" on sheet)
I was comparing the CP XIX twin with the CP XVIII
http://www.navweaps.com/Weapons/WNBR_47-45_mk9.php
Gun Length oa
Mark IX: 220.62 in (5.604 m)
Mark XII: 224.08 in (5.692 m)
4" is less than 1 pixel (6"/1 pixel) difference but the sheet has it as 6 pixels longer?
Is the Mk XI the 50 cal gun on the CPXX the last one down of the 4.7"?