If you thought that how Lady Sif dresses in Thor is how Norse women dressed, you are wrong (and possibly a misogynist). If they had dressed like that, and not like this, they would have froze off their behinds.
Not Viking. Most likely Liv/lībiešu/Livonian (a Finnic people) from Late Iron Age Latvia. Liv women wore smaller brooches with longer chains than the Norse. Do not abet the abortion of our history by buying from these brazen looters of protected historic sites. This is a crime! For a nice summary of a very thorough book on the subject of Liv/lībiešu/Livonian tortoise brooches and chain ornaments from Latvia, read here: http://briai.ku.lt/downloads/AB/12/12_137-139_Reviews.pdf