A couple questions, if i may, Marcus ...
What is the caliber (bore) ?
If those marks mean to be a date in roman numerals, why the first two are 'arabic' ?
... And are you sure those two symbols are in fact a 1 and a 3 ? Difficult to check, specially not having this barrel in hands ...
Same goes for the first symbol between the two dots; is it really a D ? Couldn't it be two separate symbols close from each other and not just one ?
... And aren't there little barrels like this one already seen here, from about the same date, although not with a date written ?
http://www.vikingsword.com/vb/showth...ghlight=cannon
Just trying to test your tolerance
M.V.G.