Hello Bahner I dont fully agree with you.
My Norwegian book do not cover Trondheim - that city is in volume 2 and I dont think that it is published yet.
The mark of June 22nd until July 22nd is 69 turned 45 degrees.
I was thinking of the mark of the Lion July 23rd until August 23rd - but it's not real right.
I also think that KM is the maker. The assayers mark is more likely to be the other one.

These marks represent Christiania (Oslo) left page is guardeins marks (assayers mark) 1719-1741 left top and 1867-1880 bottom right.
Right page is month marks March/April top left to February/March right bottom.
Most likely the Trondheim marks follow the Christiania marks - and Christiania marks followed the principle from Denmark/Copenhagen.
Regarding date I fully agree with you.