He began working with goldsmith Oluf Tostrup, the son of goldsmith Jacob Tostrup and co-owner of J. Tostrup. When Oluf Tostrup died in 1882, Prytz became formally associated with J. Tostrup. He was advanced from head designer to co-owner in 1884, after two years of study. Prytz purchased the entire company after Jacob Tostrup died in 1890, keeping the tradename.
He was born in Gravellona Lomellina, Italy. He was the son of Pehr Ambjörn Sparre af Söfdeborg (1828–1921) and Teresita Adèle Josefa Gaetana Barbavara (1844–1867). His father had served as head of the banknote printing company for the Sveriges Riksbank. He spent his early childhood with his mother at Villa Teresita in Gravellona while his father was often on business trips.
After the second world war, Jens Harald Quistgaard was apprenticed in the Georg Jensen Solvsmedie in Copenhagen. He has experimented with various media such as wood, metal, glass, steel and ceramics. Ted Nierenberg, the founder of Dansk International, noticed him because of his distinctively Danish craft aesthetic.