definitely it looks repaired , the color remains about old zink or lead .
but do you think they used an metal with an that low melting temperature as zink has ?
and I really hope that they didnt repair it with lead , I only said that the color of the repair looked like lead or zink . but what I know they often used some brass aloy to repair touch holes .
here you got 2 pictures where you clearly can see the touch hole been repaired with brass ,
Im sorry if the second picture is a bit out of focus , but you still can see the brass color of the repair .
in the first you clearly can see the marks as they have used an very narrow chissel to clean up the burnt out touch and probably also made it slightly conical ( larger closer to the bore ) before they heated the hole and poured the brass .
this barrel is cast 1665 , so its very difficult to say when the touch is repaired,
could be just a few years after the cannon was made , but could also be as late as beginning to mid 1800 .
I would guess its an early repair as this time period was a very turbulent time in the swedish history with large wars almost all the time . after 1730 it calmed down more and more .