According to the National Trust, the building at 15 Brunswick St dates from 1903 but began as the Westminster hotel (which according to the hotels in Fitzroy up to 1906 document dates from 1871). It suggests that the current building was built on the original single storey building, which may explain the different kinds of arches between the floors. It now houses a dentist.
Courtesy of J.T. Collins Collection, La Trobe Picture Collection, SLV / ID: H96.210/28 / photographer: John T. Collins / copyright: used under the fair dealings provisions of the Copyright Act 1968 / c1974