As is commonly known, the Commonwealth of Australia came into being on 1st January 1901, the first day of the Twentieth Century. On the 1st March 1901 Posts and Telegraphs came under the control of the Commonwealth Government.
For reasons we don't need to delve into here there was no universal 'Australian' stamp issue for 12 years, when the Kangaroo and Map series was issued.
The focus of this thread is, primarily, the Melbourne cancels applied to collectors sets and sets prepared for distribution to dignitaries (such as Members of Parliament).
The first Commonwealth stamps to be so prepared were the new Postage designs of the Stamps issued by the State of Victoria.
CTO stamps were, as far as I am aware, issued in all States. However, only the Victorian stamps had the Melbourne cancel applied.
Please feel free to add your CTO scans to this thread.
= = = = = = = =
Admin 2016 Edit - these are the ACSC preamble pages on the different dates and types of cancels.
The ACSC of course lists and prices all these cancels, on all stamps, in each volume they print.