mörkö was found southeast of stockholm by 2 fishermen while they was net fishing in the archpelago of stockholm , its called the Mörkö cannon because it was found just outside the island Mörkö
Im not exactly sure when it was found ( age and memory  

 ) , but I think it was 1820 or 1821
sorry 1828 it was , checked it up now and edited
its located at the historical museum in stockholm 
its difficult to date it , but today they think its from approximately 1370 +/- 10 years
for what I know of there havent been any analysis made of the metal composition 
I was actually looking for any evidence that any sample had been taking from it when I was examinating the gun , but wasnt able to find anything that looked as if that had been done
Charlotte didnt think it ever had been done
I dont know if there is any official speculations of who had made it or why 
we talked a little about it during the lunch and she agreed on my and garys theory that the head could be jesus as the writing on it is from ave maria . 
but who made it and why ?  no idea at all , cant be more than speculations .
could be a priest or a noble man , at least someone with money . 
any ordinary person couldnt afford to have it made 
at the time when it was made the church had the idea to try to christian the world , 
with weapons if neccesary . 
remember the crusades 
so your idea is as good as my , there is very little "facts" about it by obvious reasons. 
what happened from it was made until it was found can only be speculations
check the pdf , its in swedish but I guess you would be able to translate it with any translation program 
there is also some very interesting photos and drawings there