Complex sentence: Around 1854/55, it appears as a separate "eyalet", but the source is unclear; certain that in 1856 it became part of the Ioannina Eyalet, but in 1863--1867, it certainly became an "eyalet" in its own right.
Split into simpler sentences: Around 1854/55, it appears as a separate "eyalet", but the source is unclear. In 1856 it became part of the Ioannina Eyalet, but in 1863--1867, it certainly became an "eyalet" in its own right.