He then moved to Christiania (now Oslo) and acquired burghership in 1832. In 1832, he founded the jewelers firm J. Tostrup, gradually expanding his business with more production equipment and better localities.
He then relocated to Christiania (now Oslo) and secured residency in 1832. He subsequently founded the jewelry company J. Tostrup, which he grew through the acquisition of new production tools and better locations.