Couldn't withhold myself from commenting now instead of tomorrow, but this is a very attractive blunderbuss.
The brass muzzle section is, as far as i can see, only sheeted around an iron barrel mouth. When looking at the inside of the barrel mouth you can see the iron oxidation and also some small iron overlap on the brass muzzle section. Wouldn't make sence to create a all brass end for a gun, it would only cause a serious weakspot at one of the largest stress point of a barrel
The design is great looking and certainly fit for your staggering collection Nando my friend.
My position on the calibre is based on information i recieved after my own blunderbuss purchase. These guns where mainly shot with buckshot balls, so probably 10-11 mm lead balls, 10 pieces orso.
The swamped barrel mouth supports this, it wouldn't make sence with a solid lead/iron ball... blunderbussess where intended to scatter and hit as many targets at short distance. The iron looks to good for naval use i think, but who knows
What i absolutely like about this gun is the "belt" (?) hook that has survived till this day!! you don't see that to often. Take good care of this one, the market for blunderbussess has somewhat shrunk in the last few years, but such an quality item will be priceless (even more so than now) in a few years.
edit: my own blunderbuss with heavy pitted iron as comparison
http://www.vikingsword.com/vb/showth...hlight=ketland