This cannon produced by France since 1877, used by the Boers in the Second Boer War (similar model called Creusot Long Tom), used by France during WW1 (although it had obsolete carriage for that time).
Use fixed files to print. Other non-fixed files better for editing
Use netfabb or other program to check and edit files before print
Making printing supports required
You can change scale to other by yourself
scaled in mm