Shipbucket

Thanks for that. Very interesting comparison with the Hobart/Melbourne paper. Yours quotes full armament using the six hull piercings. complement much higher (95 vs 46 - gun crews?)
that would also deepen the draught.
Beam differs by 1ft? Not unknown for one source to quote maximum, another waterline.
Could tonnage 580 simply be light tonnage? there's 150tons of coal, plus crew, stores and ammunition.

"some satisfaction with repeating the design"
Indeed. From the Wiki article on Cadmus:
"The Cadmus class was a six-ship class of 10-gun[2] screw steel sloops[3] built for the Royal Navy between 1900 and 1903. This was the very last class of the Victorian Navy's multitude of sloops, gunvessels and gunboats to be constructed, and they followed the traditional pattern for 'colonial' small warships, with a full rig of sails. ... ...differed from the screw sloops of the 1860s only in an evolutionary sense."
There was even a study for similar colonial peace cruisers in 1913, design by Stanley Goodall, but rather larger 1750tons.

I've done a bit more digging. the 580 tons tonnage is probably "builders' old measurement" tonnage. That was a formula based on the extreme breadth of the hull and the length of the keel (to a vertical below the stem). It was used for early RN sloops, though originally intended as an estimate of the load carrying capacity of merchant ships (a sort of forerunner of deadweight tonnage)
p48 of W.H.White's 'Manual of Naval Architecture' explains.

My thanks to Rodondo for pushing me towards size and date of warships beyond my usual interests. Very interesting.

Only info I have, from 'Warships of WW1' by Le Fleming:

OLD GUNBOATS (and Sloops)

Of the once huge fleet of Victorian gunboats and sloops which patrolled the Seven Seas, only a handful remained in 1914. Employed in peacetime on distant Stations there duties were not greatly altered by the war.

With cruiser sterns the most modern in appearance were: Bramble, Britomart, Dwarf, and Thistle (710 tons, 1898-99). The first two were sold out of service in 1920 (at Bombay) and the other two in 1926.

More traditional in outline were Cadmus, Clio, Espiegle and Odin (1070 tons, 1900-03). These were sold in 1920-21, Cadmus at Hong Kong, and Espiegel at Bombay.

Very Similar were Rinaldo, Rosario, Shearwater and Vestal (980 tons, 1898-1900). All were sold in 1921, Rosario at Hong Kong and Shearwater in Canada. Three more ships of these last two classes were on survey duties in 1914. Fantome was sold at Sydney in 1925, Merlin sold at Hong Kong in 1923, and Mutine which lasted till 1932.

Edit:
I was hoping to find more info on the Britomart as I was aware of many places in NZ that have streets/suburbs/hills and other prominent features named Britomart. Apparently the Britomart being referred to is a colonial cruiser (sloop) of the 1840's that undertook a lot of survey work around NZ.

No worries Smurf, thanks for making me dig. And thank-you for the conversation, it's good to know whoever you are or what-ever colour the username, debate is debate and it's all for the greater good of the drawings, that's what this forum is all about

Preston, Anthony and Major, John
"Send a Gun Boat! A Study of the British Gunboat and its Role in British Policy 1854-1904" is both a history and a catalogue of RN gunboats. It has the Arrow class, but sadly not this Australian colonial ship.

Time to re-draw the oldies

Not a beautiful ship, but a lovely drawing.