Complex sentence: All came from the Rondinelli collection in Florence in around 1891, and nothing is know about their earlier provenance, apart from a claim by Rumohr, a German writer, in 1827 that they came from a Compagnia di San Zenobio attached to Florence Cathedral.
Split into simpler sentences: All came from the Rondinelli collection in Florence in around 1891. It was claimed by Rumohr, a German writer, in 1827 that they came from a Compagnia di San Zenobio attached to Florence Cathedral.