Hi Dudley,
The marking system in Norway, since 1891, has required a numerical mark to indicate silver fineness (830, 900, & 925 most commonly) and this fineness stamp to be placed in conjunction with the maker's mark. The numbers on your piece don't work for this and are likely pattern numbers, although the "27A" may be one of those arcane designations to indicate how thick is the layer of silverplate.
As to the maker, I do not know if it is Olsen, I have also been trying to identify this maker's mark. Here is an example of it on a sterling piece.
Regards, Tom
http://www.925-1000.com/Fnorway_marks.html" onclick="window.open(this.href);return false;
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