I just added another item to my Tambourine collection, which now makes two. The first was a stamp cancelled "Mount Tambourine", and is shown on the first page. That one was only the second known copy, and was the earliest, at March 24, 1924.
This new one is a complete cover for "Tambourine" and has a clear strike dated December 1, 1921.


The Queensland Steel Datestamps PDF differentiates Tambourine from Mount Tambourine. Both were later changed from Tambourine to correct spelling of Tamborine.
The earliest "Tambourine" is shown as November 12, 1918, so my copy is not the earliest known. However, Tambourine is rated as a scarcity of 4R, so a good find nonetheless.

I'll have to keep search for more, with Tambourine Mountain high on my list.