Ambrotype

She's wearing a typical Dutch necklace of bloedkoraal: red coral. (Example)

Peter Carstensen (1817-?) was a salesman from Denmark, who moved to Amsterdam in
1854 and returned to Denmark in 1868. He had a studio at Nieuwendijk H201 (1860-1868)
where he made ambrotypes and later carte de visite, before the studio was passed on to the
German Louis Robert Werner (1834-1896) who continued to make CDV there (1868-1877),
and later moved the business to Nieuwendijk 150 (1878-1886) His son Richard August Werner
worked as a photographer in Amersfoort and Amsterdam.

CDV by Carstensen/Werner can be found here.

Other ambrotype by Carstensen:

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